Personally, I would buy the Wizard's Flip Book and smack him with it.
In all seriousness, I echo what Robert was saying. Unless your school is the size of a large bathroom, there should be plenty of places to bust out a few tricks without the jerk anywhere near you.
Unless you purposely start drawing a large crowd, only then do I see a possibility that he will be attracted to the attention....like a fly on crap.
You can also make sure that you have a few self-working tricks in your arsenal, so that they don't rely on anything palmed or gaffed. That way, he can't really point out any "secret" move that you're doing.
Worse comes to worse, just perform the following trick.
1) Close your right fist
2) Cover it with a silk or hankerchief
3) Tell the jerk (in front of the audience), "And now, for my last trick, I will make a bird appear from under this cloth."
4) Quickly remove the hanky with your middle finger prominently displayed at the jerk.
5) Bask in the laughter of the crowd, or run like edited....depending on the situation and the temper of the jerk.