violence will only get you suspended or expelled. this is classic bullying that needs to be taken up with a higher authority. if you really want it to stop, you need to get someone in the faculty or administration on your side.

saying someone in the faculty won't help is bull. if they won't, get the police involved. you have to push for help just like you're having to push to get this kid to leave you alone.

the mere fact that this kid is touching you makes this physical if not sexual harassment. that is plenty reason to get someone else involved. no excuses.