Because of cerebral particularities, children may react highly sensitive to variations of nutrient supply. Therefore, an optimised composition of meals at favourable mealtime should be considered for optimal cognitive performance. The increasing implementation of all-day schools in Germany requires the children's catering for lunch at school. However, the number of 'meal skippers' is increasing among children and adolescents. Thus, the effect of skipping lunch at school on cognitive functioning is examined in this experimental cross-over trial. As prior intake of food can have an influence on the physiological effect of test meal, the children's dietary intake in the mid-morning is standardized. The intervention is integrated in everyday school life: