Teaching and apple symbol?

Question

When and why did teaching and teachers come to be associated with apples as a symbol?

Answer 1

In the United States, Denmark and Sweden, an apple (polished) is a traditional gift for a teacher. This stemmed from the fact that teachers during the 16th to 18th centuries were poorly paid, so parents would compensate the teacher by providing food. As apples were a very common crop, teachers would often be given baskets of apples by students. As wages increased, the quantity of apples was toned down to a single fruit.

Answer 2

I figure, 'an apple a day keeps the doctor away', I did not want my teacher to get an apple.