You have to have independent witnesses, so find your support group, and have them keep an eye on what he gets up to when he is around you. Then, with witnesses, you can go to the authorities and demand justice.

Harrassing you in what way? Sexually - actual touch or just what he talks about? Physically - tapping the back of your chair or something? How old are you, if you don't mind my asking? Teen or college? When I was a pre-teen and early teen I was harrassed by the boys in my class. They felt me up, they talked lewdly and crudely about my body. I didn't know what to do. Looking back, I should have told the teachers, but I was just too scared to, I didn't know that I could tell someone. It didn't just happen to me, it happened to everyone. I thought that was normal behaviour. If I were you, I'd tell whoever the authority/teacher in the class is, and let them set about a mediation process. Otherwise, I'd start thinking up some seriously brutal put-downs and put him on the back-foot. I'd make sure that other members of the class know what's going on, so that they can help you get him to leave you alone. Once he realises that other people know what he's doing, he may shrink back from doing it, feel embarrassed.

Here's a slightly different perspective on the situation, based on experience. It could easily be the case that this guy is autistic to some degree. Many people at the near end of the Autism spectrum function perfectly well in society, but have certain behavioural issues. One of these is that they DO appear to be harassing others, and another is that they WILL deny wrongdoing, even when presented with incontrivertible evidence. It may be the case that taking a little bit of time to understand where this person is coming from and taking time to explain how you feel could solve your problem without recourse to stronger measures. Please remember that there are two sides to every story and we often need to hold a mirror up to the situation to get a real understanding.

Since you didn't give us much to go on here...I would also suggest that you ask yourself if it is possible that YOUR perspective of the TRUTH, that you have confronted him with...is perhaps not HIS perspective of the truth. Not to say that YOU are lying but that I don't know what you consider the truth to be in this case. The bottom line, however, is CLEAR. You come to school to learn those things which you are either expected to learn (High School, Jr. High, Grade School) or that you are PAYING TO LEARN...at College level. HIS behavior is causing YOU disruption in your learning and he does NOT have the right to do that! You need to speak to your teacher after class. If the teacher does nothing to stop it. (change of seating perhaps) then you speak to your Councilor about it, AND YOUR PARENTS if you are in High School or lower grades. If that doesn't fix the problem, you have your PARENTS visit the school and speak with the Vice Principal. YOU are allowed (in my opinion) to also verbally, loudly, and clearly speak up in class, "STOP (whatever IT is he is doing) TOUCHING ME, BOTHERING ME...I AM TRYING TO PAY ATTENTION HERE! That should give your teacher cause to do something...especially if you have already discussed it and they have done nothing! Enough is Enough...be sure YOUR behavior is beyond reproach in this matter...do not encourage or egg him on in his behaviors, but do not allow yourself to be abused by a bully or trouble maker either!

I would make sure to always have someone with me to be a witness. Make sure you don't sit anywhere near him and make sure your teacher is aware of the problem. Pursue legal means if necessary.