system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is there an association between teachers and apples?

Also, I've noticed it's specifically red apples.
gpt
Long ago, teachers were paid by the families of students, rather than the government.  Some families could not afford to pay the teachers, so they made arrangements to give the teachers excess crops from their farms instead.  Apples were a common crop used for this purpose.  

So why is it an apple instead of any other fruit or vegetable?  One idea is that apples used to be used for making cider, which adults liked, and after the temperance (anti-alcohol) movement, apples' reputation switched to that of a healthy food.  ("An apple a day keeps the doctor away.")  This kept apples as a commonly accepted thing to give to a teacher.  Another explanation is that apples are associated with the Tree of Knowledge from the biblical story of Adam and Eve, so apples could be viewed as a symbol of knowledge, which would be appropriate for an educator.