[T-nex]

pretty much what Ghost said. tell a teacher. if they don't bother resolving it, go to another one. whilst you're in school people should be there to help you. that doesn't last forever, so use it.

on the other hand, don't delude yourself into thinking you're completely defenseless, no one is made of porcelain. if it comes to it, fight back and kick his arse. you're in the right. as long as you're merely defending yourself and the school staff aren't complete wankers, you shouldn't get into trouble for it.

or just say he has a small penis.

Kick his nuts :3

If it's a girl.. punch her tits!