I think you need to go directly to your principal, who would then tell your teacher. Things like this need to be taken care of the moment it happens - I know most people freeze and think it won't happen again. I have 2 daughters almost 10 and 14. My 14 yrs old is a black belt in karate. Most of the guys around her know they can't get away with saying or trying to touch her, because she will / can defend herself.

You said if he does this you'll snap - don't wait or let it build. Be proactive and go directly to your principal. You can also learn how to walk and talk with confidence - others can sense if you might not tell or can be victimized. I've instilled this confidence in my girls and I'm passing this onto you now. Its your body. Tell the principal if this isn't taken care of, you'll then call the police.