Why is an apple a symbol of a teacher?
The apple is not a symbol of the teacher directly but of the
knowledge the teacher imparts to the students.
Apples have been considered a symbol of knowledge mainly due to
the common belief that it was an apple that Eve pulled from the
forbidden tree of knowledge to give to Adam.
It is also in this origin that the term "Adams apple" (referring
to the bump sometimes seen in a males throat) came to be. The story
is told that the apple became stuck in Adams throat once he
realized it was wrong.