Okay honey, this is my opinion. Don't be afraid to say something to a principal or teacher... you should probably say something to your parents first. That is sexual harassment and your school should not put up with it... the adult world doesn't. I can't think of one line of work, with respectable jobs of course, that puts up with sexual harassment. You can have his classes changed so that he's not in any of yours. All you really have to do is say that you're scared he's going to take his gawking one step too far and you fear for your safety. Stand up and be strong, this should not be tolerated! You can't trust people who don't respect your space.
Kris