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AN ANLYSIS OF COHESION OF EXPOSITION TEXTS: AN INDONESIAN CONTEXT

The paper reports on the results of a study aiming to investigate the cohesion of exposition texts written by eleventh graders of a school in Bandung, West Java, Indonesia. The study used a qualitative case study research design, especially text analysis, involving 32 students. In the interest of space, the paper will present the data obtained from six texts written by 6 students, representing low, mid, and high achievers. The texts were analyzed using systemic functional linguistics (SFL), especially in terms of schematic structure and linguistic features, especially those contributing to the cohesion of the texts, such as Theme progression and cohesive devices. The results show that all texts show students’ grasp and understanding of the schematic structure of an exposition, including thesis, argument, and restatement of the thesis. All texts also successfully use the zig-zag and the Theme reiteration patterns, which indicate the students’ emerging capacity to create a text with cohesion at the clause level. However, only texts written by high achievers employ the multiple Theme pattern, indicating the students’ emerging capacity to create a text with better sense of connectedness, unity, and flow of information at the global level. High achiever texts also employ discourse features which allow the reader to predict how the text will unfold and guide them to a line of understanding of a text as a whole. Moreover, in terms of cohesive devices, all texts use some simple cohesive devices—reference, lexical cohesion, and conjunction. It should be mentioned that all texts are rudimentary with some inappropriate word choices and grammatical problems. This suggests that the students still needed more guidance and time to do research on the topic in focus, to go through the process of writing as professional do, to allow them to create a better text with more elaboration and characteristics of written language with consistency and accuracy. It is recommended that further research on different perspectives and foci of analysis of different text types using systemic functional linguistics, with more representative samples, and studies on the teaching of writing be conducted.

In all educational levels, students are required to engage with many texts. In primary school, the typical texts they encounter are related to stories (Martin & Rose, 2008). As they move to the higher level of education-secondary school-the texts they encounter during their study are getting more complex.
In secondary school, students' accomplishment in fulfilling advanced literacy tasks, as Schleppegrell (2004) suggests, is indicated by the way they use language to construct more condensed and specific information from their surroundings that is different from their everyday pattern of interaction at home or in the neighborhood. Such condensed and specific information can be realized into various types of texts, one of which is exposition.
In Indonesia, all students in senior high school are expected to have the capacity to comprehend and to write exposition texts, as stipulated in the 2013 English Curriculum (Ministry of Education Regulation, No. 64 Year 2013). Such policy goes with the salient point of writing an exposition text for students' academic success and their effective social participation (Crowhurst, 1990;Knapp & Watkins, 2005). The ability to compose argumentative text (including exposition), as Bizzel (1992 as cited in Emilia, 2005) argues, can help develop students' critical thinking which can eventually lead the students to be powerful and competitive individuals.
However, to write an exposition text is not easy for EFL students. Common problems found in composing an exposition text are misuses of cohesive devices, as reported by Chen (2008). For Indonesian EFL students, the exposure to such an argumentative genre is still limited in both their doi: 10.17509/ijal.v7i3.9791 native tongue and English. Many Indonesian students, based on the writers' observation in the classroom, struggle to write an effective exposition text, especially to employ the textual resourcestheme progression and cohesive links-in the text. This condition may lead to different understanding of how they should construct an effective exposition text in English. Regarding this, Hawes and Thomas (2012) point out that there would be any particular differences between the structure of the exposition text in their first language and the one written in English, especially with regard to the use of textual resources that include the use of Theme progression and cohesive links to create an effective text with a good flow of information (Droga & Humphrey, 2003;Derewianka & Jones, 2012 for a similar discussion).
Studies on the use of cohesive devices in EFL students' texts have shown that students still encountered some problems in using appropriate cohesive devices. Students tend to focus on the word or clause level rather than the whole discourse level (Ferris & Hedgecock, 1998 as cited in Lee, 2002) in creating an exposition text. The problem was also found in more recent studies conducted by Chen (2008), Witte and Faigley (2008), Azzouz (2009), Dastjerdi andSamian (2011), Sanczyk (2010), Ong (2011), andSidighi andHeydari (2012). They reported that there were still some problems of cohesive devices employment in an argumentative genre written by EFL students, leading to the failure of shaping an effective flow of information. As far as the flow of information is concerned, utilizing cohesive analysis has several advantages. The development of cohesive devices in students' texts has a significant impact on the writing quality (Crossley, Kyle and McNamara, 2016). In addition, cohesive analysis plays an important role in identifying specific ways of discourse features which guide the reader to a line of understanding of a text as a whole (Bastrukmen & von Randow, 2014). Based on the previous elaboration of the importance of cohesive devices in argumentative writing, this study aims to investigate the cohesion of students' exposition texts, seen from the schematic structure, and linguistic features, especially to do with Theme progression, and cohesive devices.
This study has been informed mainly by systemic functional linguistics, especially to do with cohesion, and exposition. Those theories will be delineated below.
Systemic functional linguistics is a social theory of language developed by Halliday (1994). SFL holds the principle that all languages have three meta functions: textual, ideational, and interpersonal metafunctions. Each function is realised in a different pattern of grammar. Textual metafucntion, a unit of which is cohesion, with which this paper is concerned, is realised in the Theme system, referring to what is fore grounded. The Theme system is realised through a structure in which the clause falls into just two main constituents: a Theme and a Rheme. A Theme is the element which comes first in the clause, or "what the clause is going to be about" (Eggins, 1994, p. 275). It is "the point of departure of the message" (Halliday, 1994, p. 37;Halliday & Mathiessen, 2004, p. 64). Meanwhile, the Rheme is "the part of the clause in which the Theme is developed or everything that is not the Theme is the Rheme" (Eggins, 1994, p. 275).
In line with the metafunctions of language, there are three types of Theme, including: topical Theme (related to ideational metafunction), textual Theme (related to textual metafunction), and interpersonal Theme (related to interpersonal metafunction).
Apart from the Theme of a clause or a sentence, there are also higher-level Themes, including hyper-Theme and macro-Theme. Hyper-Theme is the Theme of a paragraph, an introductory sentence or group of sentences, established to predict a particular pattern of interaction among strings, chains. Macro-Theme can be defined as a sentence or group of sentences (possibly a paragraph which predicts a set of hyper-Themes). This is the Introductory paragraph of school rhetoric (Martin, 1992, p. 437;2002, see also Martin & Rose, 2003).
Cohesion is considered an internal element, which binds the passage together (Halliday & Hasan, 1976). It is one of the hints for the reader to relate the meaning together within the text (Dastjerdi & Samian, 2011). In functional linguistic terms, cohesion is considered a non-structural unit of textual metafunction. Non-structural unit, as stated by Halliday and Hasan (1976), means that cohesion does not depend on the structural unit in the text, such as clause or sentence. Cohesion is located beyond the sentence or the clause, which is meaning. Halliday and Hasan (1976) further explain that cohesion plays a central role in creating a sense of connectedness and unity of the text because the interpretation of some elements in the text depends on one element to another--defining text as a text (see also Martin, 1992;Eggins, 2004;Emilia, 2014). In order to achieve the sense of connectedness and unity, the semantic relation internal to the text, namely cohesive device has a significant influence to maintain interrelation between meaning in the text (Halliday & Hasan, 1976;Gerot & Wignel, 1994;Eggins, 2004;Emilia, 2014) in order to relate between items as the text develops (Derewianka & Jones, 2012).
Cohesive devices which are focused in the study include references, lexical cohesion, conjunctions, ellipses, and substitutions which will be discussed below.
Reference means "pointing" to something mentioned elsewhere in the text (Derewianka & Jones, 2012). Reference is a system to which the identity of item is introduced and tracked through text (Gerot & Wignell, 1994). According to Eggins (2004), reference is retrievable from a number of different contexts: homophoric, exophoric, and endophoric references (see also Gerot & Wignell, 1994). The endophoric reference will be a focus of discussion in this paper as it is crucial in the creation of text's cohesion (Eggins, 2004;Halliday & Hasan, 1976) which is the focus of the study.
Endophoric is known as a reference which can be recalled from within a text (Bloor & Bloor, 2004;Eggins, 2004;Halliday & Matthiessen, 2004;Christie & Derewianka, 2008;Emilia, 2014). Eggins (2004) categorizes Endophoric into three types: Anaphoric or "backwarding looking"; Cataphoric or "forward looking"; and Esphoric which occurs when the occurrence of the referent in the phrase follows immediately the presuming referent item (within the same nominal group/ noun phrase in a separate clause).
Conjunction or conjunctive relation, as stated by Eggins (2004, p.47), is a term used to describe "how the writer coins and expresses logical relationships between parts of the text". Halliday (2000) categorises conjunctions into three, including elaboration (e.g. in other words, that is, I mean, to put in other way, for example, for instance, thus, at least, in short, actually), extension (e.g. and, moreover, nor, but, yet, on the contrary, apart from that, alternatively), and enhancement (e.g. secondly, similarly, in a different way, so, then, therefore, but, yet, still, because).
Ellipsis is the omission of words, groups or clauses (Bloor & Bloor, 2004;Emilia, 2014), and substitution is a term used to replace a component of clause with a shorter word such as one, some, do (Droga & Humphrey, 2003). The substitution occurs in order to substitute a word, phrase, or clause instead of repeating them elsewhere in the text (Droga & Humphrey, 2003;Bloor & Bloor, 2004;Carter & McCarthy, 2006, as cited in Emilia, 2014. Another aspect of cohesion which has informed this study is Theme progression which is a thematic development which aims at creating cohesion and coherence of the text (Eggins, 2004). The employment of Thematic progression can help the writers organize and develop their ideas or information smoothly (Emilia, 2014). There are three categories of theme progression patterns: the zigzag pattern, the Theme-reiteration pattern, and multiple Theme pattern (Eggins, 2004; see Bloor & Bloor, 2004 for similar discussion). Each type will be alluded to later in the discussion of sample texts.
The last theory from which the study has been drawn is exposition. Exposition is a piece of text that aims at persuading the readers or the listeners by presenting arguments for a single position or view (Anderson & Anderson, 1997;Martin & Rose, 2008). There are two kinds of exposition: Analytical and Hortatory expositions (Derewianka & Jones, 2012;Emilia, 2014). When the writer might be arguing simply to justify a position or an interpretation (persuading that), it is called analytical exposition. Moreover, when the writer might be arguing that some sort of action should be taken (persuading to) or set out to persuade the reader or the listener to act in particular way, then it is called Hortatory exposition (see Derewianka, 1990;Coffin, 2006;Martin & Rose, 2008;Derewianka & Jones 2012).
To achieve its social purpose, exposition text follows three essential stages, which are thesis announcing the issues or topic being concerned (Gerot & Wignell, 1994) in which the author gives point of view and previews of the argument that will follow (Anderson & Anderson,1997); arguments supporting the thesis by giving evidence and examples (Derewianka, 1990;Coffin, 2006); and restatement of the thesis or conclusion summing up the arguments and reinforcing the writers' point of view (Anderson & Anderson, 1997) (see Martin & Rose, 2008;Emilia, 2011, for detailed elaboration on argumentative genre families and their stages).

METHOD
This study utilized a qualitative case study research design especially text analysis. The study involved a teacher and one class consisting of 32 students, categorized into low (with the English score 30-50), mid (60-79), and high achievers (80-100) by the teacher. The participation of the teacher and the students was voluntary. In the interest of space, the teaching learning process cannot be presented in this paper, and only 6 texts analysed in detail in the study. The process of text collection can be described in several steps below.
First, the students were given four topics of writing; the importance of doing exercise, the dangerous of fast food, playing games in spare time, the importance of wearing helmet and saving money from the early age. Those topics were chosen because they were current issues that students encountered in their daily life.
Second, the students chose one topic and wrote an exposition text about it. It should be mentioned that the students wrote the text only one time within 2 hours in the classroom. This is one of the limitations of the study, that the students were not given an opportunity to experience the process of writing as professional writers do, going through the recursive process of writing: drafting, revising, editing, proofreading. The students could have produced better texts if they had been given more time and guidance.
Finally, the students' texts were selected, and with the help of the teacher, were classified into three different levels of achievement, as presented in Table 1. Table 1. Categories of achievement and Topics of exposition.

Categories of achievement Text Topic
Low achiever Text 1 Playing video games in spare time Text 1a The danger of fast food Middle achiever Text 2 Learn to save money from early age Text 2a The importance of wearing helmet High achiever Text 3 The dangerous of fast food Text 3a The importance of doing exercise Those texts were analyzed using systemic functional linguistics, especially terms of the schematic structure and linguistic features, including types of cohesive devices and Theme progression patterns. The analysis was conducted in steps, and will be elaborated below.
First, the texts were analysed in terms of the schematic structure, including thesis, arguments and restatement of the thesis. In the interest of space, only one text from each level of achievement will be presented in this paper.
The analysis of the students texts representing low, mid, and high achievers will be presented in the discussion section, and the texts analyzed into clauses can be seen in Tables 2, 3, and 4 in the discussion section.
Third, the texts were analyzed in terms of linguistic features, especially aspects of cohesion, including:  Reference chain e.g.  (2) damage (text 3a) -Hyponymy chain, e.g. (3)Video game - (3) action game (text 1) -Co-hyponymy, e.g. (6) cancer - (6) Disease (text 3) -Meronymy, e.g. (9) body-(10) digestive-(12) immune-(15) brain (text 1) -Co-meronymy,e.g. (10) digestive- (10) body (text 3)  Conjunction, underlined and written in italic. e.g. But fast food is rich of sodium and the harmful additive (text1)  Ellipsis and substitution, identified by marking single asterisk (*), e.g. Why?* (Text 4) This analysis aimed at investigating the realization of cohesive devices in students' texts and how those cohesive devices contribute to the creation of effective flow of information in the texts. Finally, the texts were analysed in terms of Theme progression patterns to identify the text organization and cohesion at the clause and text levels. To follow Eggins (2004) and Emilia (2014), the theme progression was categoriezed into the zig-zag pattern, the Theme reiteration pattern, and the multiple Theme pattern. The sample of each pattern can be seen below.
 The zig-zag pattern Text 3 (9) Second, the additive in fast food are isolate for our body (11)They turn into poison to our body The example of multiple Theme pattern can be seen later in the discussion of high achiever text, as this pattern was found only in the texts written by high achievers.

FINDINGS AND DISCUSSION
The result of the analysis will be presented in terms of schematic structure and linguistics features, especially to do with cohesion and theme progression. The discussion will be based on each element of each text.

Text 1 written by low-achiever student
Text 1, written by low achiever can be seen in Table  2. . we can play video games 6. because it make(s)our brain feel so fresh 7. after we doing (do) so many of jobs (much work).

Restatement of the thesis or conclusion
8. So start now 9. to playing (play) video games in spare time. 10. It is the best strategy [[to balance between physical activity, exercise the brain (brain exercise), and social interaction]] .

Notes for the text above and other texts in this paper: [[ ]]
indicates embedded clause; underlined parts of clauses are Theme of the clauses (with the words in italics being textual Themes) to identify the cohesion and Thematic progression of the text; words in brackets ( ) are the correction made by the writers.
The text has all elements of exposition, which are thesis, arguments, and restatement of the thesis, as pointed out by Christie and Derewianka (2008) and other theorists mentioned above.
The text begins with an opening topic-based, which is playing video games. Subsequent Themes in the text are mainly categorized into multiple Themes, consisting of textual and topical themes (if we, because we, after we). The use of textual Themes, realized in conjunctions above, helps maintain the connectedness of idea at the local or clause level. The topic playing video games which is thematised in several clauses also indicates the writer's effort to foreground items to do with the topic.
With respect to Thematic progression, the text uses two types of Thematic progression as suggested by Eggins (2004), including the zig-zag and the reiteration patterns. An example of each pattern can be seen below:  The zig-zag pattern can be seen in clauses 5-6, when participants of the Rheme of clause 5 becomes the Theme in clause 6 using the reference it.
(5) We can play video game (6) because it make(s)our brain [[ feel so fresh]]a  The reiteration pattern (clauses 1-2) when the Theme of clause 1 repeatedly becomes the Theme of subsequent clauses. This also occurs in clauses 4-5, when we as the Theme of the clauses.
(1) Playing video games is good for us (2)  Overall, the Theme choice suggests the writer's effort to foreground items more specifically to do with the topic under consideration, that is playing games (McCarthy & Carter, 1994, p. 75 in Emilia, 2005. In terms of cohesive devices, which are also relevant to the Theme choices presented above, the text successfully employs several cohesive devices, especially in argument and restatement of the thesis elements. These include conjunctions as a textual Theme to elaborate the writer's idea: such as if, because, so, and after (see clauses 4, 6, 7, 8 respectively).
The employment of these conjunctions strengthens the unity and connectedness of the messages (Emilia, 2005). Moreover, the text uses some referential items which serve to trace ideas or participants e.g. first personal pronoun us, we, and third personal pronoun it. However, the presence of the first person pronouns Thematised (see clauses 4,5, and 7) like we suggests the students still need guidance to develop a clearer accent of written usage (Martin, 1992). The first personal pronouns indicate a subjective opinion (Knapp & Watkins, 2005) and create a sense of personal relationship between the writer and the reader. However, the last sentence of the text indicates that the writer has successfully employed impersonal pronoun it which makes the text "more-written like" (Eggins, 2004) and shows that the writer strives to foreground objectivity in presenting the proposition (Emilia, 2005).

Text 2 written by middle-achiever student
Text 2 written by middle achiever can be seen in Table 3.

Conclusion or restatement of the thesis
17. So, we should try this method to our children. 18. So, they could be a thrifty person in the future.
As shown in the Table 3, similar to the text written by low achiever, the text written by the middle achiever has shown the essential elements of exposition text as mentioned above. However, this text, unlike the text written by low achiever, provides some background information of the issue under discussion before stating the thesis statement.
The text commences with a marked topical Theme, realized in a Circumstance: At this time, there are so many people [[that (who) always waste their money]]. The use of this marked topical theme indicates that the writer foregrounds the time as the departure in the direction of the discourse (Emilia, 2005). Subsequent Themes in the text are categorized into unmarked topical Themes, many of which are combined with textual Themes, realized in the use of several textual strategies that will be presented later.
The text, similar to that written by low achiever presented earlier, uses two types of Theme progression patterns, the zig-zag and the reiteration patterns.
Overall, the choices of Theme of the clause suggested the writer's effort to maintain connectedness between clauses. However, at the global level, the texts written by low and middle achievers do not develop effectively because they do not efficiently manipulate a multiple-Theme development which shows a feature of written mode (Emilia, 2014, p.258).
Regarding cohesive devices, which are still relevant to Theme choices presented earlier, the text successfully employs several textual strategies in all elements of the text. These include conjunctions as textual devices to maintain logical connectedness between propositions expressed in clauses, such as so and because (clauses 5, 11, 16, 17) which hold an elaboration role; whereas (clause 4) which has a contrastive role; and conjunction and (clauses 7 and 12) which has an additive role.
Moreover, other textual strategy used in this text is reference, which includes referential items of possessive determiner their (clauses 3, 4, 10, 11, and 15), and personal pronoun they (clauses 4 and 18) and we (clause 17), which serve to trace ideas or participants. However, it should be mentioned that the frequency of the use of the first person pronoun we in this text is lower than the text written by low achiever. Infrequent use of personal pronouns indicates the writer's capacity to produce a text which is more written like and shows emerging capacity to express ideas in academic persuasive genre (Humphrey, 2017, p. 29-30). In addition, the use of pronoun we in the last element shows that the writer prefers personal voice to impersonal voice to persuade the readers (Chen, 2008;Dastjerdi & Samian, 2011).
The last textual strategy used in the text is whellipsis of the whole clause, which is realized in clause 13. The use of this ellipsis indicates that the writer has achieved economy by avoiding the repetition of lexical elements that can be retrieved or understood by the reader by what has proceeded or what has followed the ellipsis item (Knapp & Watkins, 2005, p. 50-51).

Text 3 written by high-achiever student
Text 3 written by high achiever student can be seen in Table 4.
The text written also shows all elements of exposition text, including thesis, arguments, and restatement of the thesis. Similar to the text written by middle achiever, this text provides some background information of the topic under consideration which leads the reader to the thesis statement.
The text is opened with some background information which is signaled by a marked topical Theme, realized in Circumstance These days, there are many fast foods restaurants in everywhere, which shows that the writer emphasizes time as the departure in the direction of the discourse. The text is then followed by the thesis statement.
Conspicuous is that the text, unlike the previous ones, overtly signals its elements with appropriate linguistic resources to create a successfully-organized text through the employment of a multiple-Theme pattern with the introduction of the text functioning as a macro-Theme (clause 5). This macro-Theme, which is the introduction of the text as a whole, is followed by hyper-Themes (topic sentence of a paragraph), and these hyper-Themes are explicitly signaled with appropriate linguistic features (temporal connectives first, second, third). The use of these connectives (clauses 6, 9, 13) helps the text to move forward very easily. Table 4. Text 3 written by high achiever Thesis 1. These days, there are many fast foods restaurants in (in should be omitted) everywhere 2. Fast food is practical, 3. and we can find it easily. 4. So many people like it. 5. However, eating fast foods has negative effects Arguments 6. First, fast food makes obesity. 7. Fast food almost contains 'zero' nutrition value, 8. but fast food is rich of sodium and the harmful additive 9. Second, the additives in fast food are isolate (isolated) in our body. 10. They become stranger in our digestive system. 11. They turn into poison to our body. 12. And finally they lower our immune 13. The multiple-Theme pattern in the text can be seen below. The macro-Theme (Clause 5) is the highest level of Theme or the highest "hierarchy of periodicity" (Martin & Rose, 2003, p. 193) that allows the readers to predict the set of hyper-Themes in the text as a whole (Emilia, 2014, p. 258). The macro-Theme is very crucial as it serves to signal and establish for the kind of the text that will unfold. The employment of multiple-Theme pattern indicates that the high achiever student had emerging capacity to develop textual strategy that works at the global level (Emilia, 2014).
In terms of cohesive devices, which are also relevant to the Theme choices presented above, the text successfully applies cohesive devices, especially in argument and restatement of the thesis elements. In the argument stage, the text is organized through the help of hyper-Themes (topic sentence of a paragraph), through the use of temporal connectives first, second, third, and third. These connectives are significant to maintain logical relations and to link points (Knapp & Watkins, 2005). Moreover, some referential items such as personal pronoun they (clause 10 and 11) and it (clause 12) and demonstrative pronoun the (clause 9) serve to trace ideas or participants.
Overall, the use of cohesive devices and higher level Theme allows the text to develop efficiently not only locally, but also globally, indicated by the presence of macro-Theme and hyper-Themes.

Cohesive Devices Consistency
As can be seen in Table 5, students from all different proficiency levels have started to make efforts to employ various cohesive devices in composing an exposition text. Table 5 shows that lexical cohesion is the most frequently used cohesive device in students' texts. It occurs 134 times in six students' texts. This corresponds to the results of other studies conducted by Chen (2008), Sanczyk (2010), Dastjerdi and Samian (2011), and Saudin (2013) on the frequent use of lexical cohesion in argumentative genre. The use of such lexical cohesion strengthens the internal connectedness of the text by gradually expanding and shifting its textual meaning (Eggins, 2004, p. 52).
The occurrence of lexical cohesion is followed by conjunction and reference respectively, with the number of occurrence of conjunction being 48 times and reference 47 times. The employment of conjunction in the text has significant contribution to the text's unity and its logical relation between clauses (Emilia, 2014). Moreover, the use of reference keeps the track of the things or participants presented. High-Achiever Middle-Achiever Low-Achiever Total  1  2  3  4  5  6  Reference  8  11  5  19  2  2  47  Lexical cohesion  26  30  24  24  12  18  134  Conjunction  12  8  11  8  5  4  48  Ellipses  ---1 -- The least occurrence of cohesive devices is ellipsis and substitution. Ellipsis occurs once and substitution is absent in all the texts. The reason for the least occurrence of ellipsis and the absence of substitution is that those cohesive devices mostly exist in conversation or dialogic text than in written discourse (see also Witte & Faigley, 2008, p.190). Thus, in this aspect, all texts have started to show their understanding of characteristics of written texts.

Theme Progression Consistency
As discussed above, in terms of Theme progression, all texts employ the zig-zag and the Theme reiteration patterns. However, only high achievers could apply the multiple Theme pattern.
The occurrence of each Theme progression pattern varies, and the highest occurrence is the zigzag pattern. This shows that all texts reflects the students' emerging capacity to build a sense of cumulative development of information in that newly information introduced from the previous information found in the preceding clauses (Eggins, 2004;Emilia, 2014).
The second Thematic progression pattern that occurs frequently in all texts is the reiteration pattern. The use of the reiteration pattern indicates that the students have a strong awareness of keeping the information flow in a clear manner by repeating the use of similar topical Theme (Eggins, 2004;Emilia, 2014) to allow the reader to find information easily.
The last Thematic progression pattern that is used only in texts written by high achievers is the multiple-Theme pattern. The use of this pattern signals that high-achiever students have carefully planned their writings in a sense that the ideas are organized into a clear sequence as the text unfolds to guide the reader to a line of information as a whole.
All these suggest the need for explicit teaching to allow all students have a similar capacity to create a successfully-written text.

CONCLUSION
This paper has presented the results of a study on cohesion of texts written by eleventh graders in a school, in Bandung, West Java, Indonesia. The study analysed 6 texts written by 6 students, representing low, mid, and high achievers, categorized by the teacher. The texts were analyzed using systemic functional linguistics (SFL), especially in terms of schematic structure and linguistic features, especially those to do with cohesion.
The results show that all texts show all elements of an exposition, including thesis, argument, and restatement of the thesis. This indicates, to some extent, students' grasp and understanding of the demand of the generic form of an academic exposition genre, to achieve the purpose and the function of the genre. However, only texts written by high achievers overtly signal the elements with appropriate linguistic resources or discourse features which can create global cohesion and guide the reader to a line of understanding of information as a whole.
Regarding Thematic progression, all students have started to make efforts to write a cohesive text, especially at the local or clause level, through the use of the zig-zag and the Theme reiteration patterns. However, only high achievers could apply the multiple Theme pattern, which suggests their emerging capacity to create a successfully-organized and well-planned text with a better sense of connectedness, unity, and flow of information at the text or global level.
Moreover, in terms of cohesive devices, all students started to use some simple cohesive devices-reference, lexical cohesion, and conjunction. Lexical cohesion is used by the students more frequently than conjunctions, references, ellipses, and substitutions.
It should be mentioned that all texts are still rudimentary, and have inappropriate word choices and grammatical mistakes. This suggests that the students still needed more guidance and time to research the topic in focus, to allow them to a create longer and more elaborate text with more characteristics of written language and argumentative discourse with consistency and accuracy.
It is then recommended that further research involving more text types and foci of analysis and more participants in different contexts in Indonesia be conducted. A close look at the time allocation for English in high school, the teaching of writing different text types as suggested in the 2013 English curriculum, and the role of explicit teaching to guide students to write successfully-written texts should also be conducted.