Is it permissible to accept a student's gift to a teacher?

If the student's gift to the teacher is intended to curry favor in exam grades, then it is forbidden for the teacher to accept it because it is considered a bribe. The teacher must fulfill his trust, for he is responsible for it and will be held accountable for neglecting it. This gift may also be considered ghulool (unlawful acquisition from war booty or public funds, or, more generally, embezzlement or betrayal of trust).