Zeronet has the right sort of idea, kasperl. (Well, not in the details, since you don't want to be expelled.) The power of group mockery lies in the one being mocked accepting the words as a put-down. The key to disarming the enemy is to be amused by their comments, rather than hurt. If you find it funny, and engage in some light joking along those very lines, suddenly you've turned their sword into a playtoy, and what was meant to cut you down is now building you up.
The social dynamic at work here is this: they take a tone of mockery and condescension, and we all too often accept without thinking the shame that they are trying to impose on us. If they mock us, and instead of shame we respond with laughter, the force of mockery is taken away from them, and they can either shut up and look stupid, or be transformed into fellow jokesters who have to grant you respect.
There is no cure like full-hearted laughter.