Good reasons to be informed of your gpa include all of the following except

student athletes must maintain at least a 2.0 to be eligible to compete.
many scholarships and grants for college use gpa to decide their awards.
auto insurance rates can be reduced if you have a good gpa.
so you can compare yourself with your friends.

the answer to the question is punishment. or more specifically, positive punishment.

positive punishment occurs when a behavior is given a negative consequence for the individual doing the behavior.

sara no longer wants to ask questions (the behavior) because she is ridiculed by mr. smith (the punishment).

reinforcement is inaccurate because reinforcement always gives positive consequences for the individual doing the behavior, be it by introducing a pleasant consequence or removing an unpleasant one.