Stalker need help!!!

OK I'm having boy trouble and it isn't the oh how do I tell him I like him thing, it's how do I tell him to knock it off?

OK it started when we were in the 6th grade, we're seniors now, so you can see my problem. My problem is that the boy is complete stalker.

Now I'll only tell you his first name because many people have that first name, so I won't exactly be putting him out there.

OK this is how it started one day all of the kids in class started telling me, "Hey Isaac likes you" and I kind of ignored them because of how kids like to play jokes and say that someone likes you when they don't and secondly I didn't know who Isaac was, I was one of those people who might have seen you but I don't know your name, you know one of those people who knows your name, but doesn't pay attention enough to match it up with your face,but by the end of the year I knew everyone.

anyway I find out who the kid is and he's really nice he's sweet and all, but I wasn't allowed to date, so I had turn him down so later that week, everyone kept asking how is your boyfriend and I didn't know what they were talking about and they said Isaac, I told them Isaac wasn't my boyfriend and they all told me that Isaac was going around telling everyone that I was his girlfriend, so I had to set them straight, now at this point I'm kind of annoyed then later I find out that he's told the kids that we are back together when we were never together in the first place and now I'm officially annoyed with this kid so I tell him flat out in front of everybody that I'm not his girlfriend and he needs to stop it.

So next a new girl comes to school and I make friends with her, now this is were he really annoyed me because now he starts going out with her and don't get me wrong it's not the fact that they dated that bothered me because finally I think he's over me and, that he'll leave me alone, but since she's new unlike my other friends she doesn't know not to give the boy my number, so now he's calling my cellphone so I have to get my number changed and put his number on my block list on my new phone and then she breaks up with him because he can't stop asking her questions about me.

So after the break up he starts the I'm going be annoying to get your attention thing, you know making fun of me and stuff. in middle school we had all the same classes because your class never separated they were just getting us used to changing classes so I won't comment on that, but constantly trying to sit next to me, behind me or in front of me is kind of annoying.

So now we are in high school about to graduate and even though he only has two classes together he somehow finds his way to basically walking me to class everyday even if he passes his class or if the class he's having that period isn't even on the same floor. His locker in down stairs and mine is up, but somehow he always finds his way by my locker everyday and he constantly gets into fights with my boyfriend for no reason.

Now I kind of feel bad for the boy because some of the kids do kind of pick on him and I guess it's kind of my fault for being nice, but if he doesn't stop I think my boyfriend might actually hurt him I mean usually when they fight it's just and argument or my boyfriend will just put him in headlock or some kid of hold after Isaac tries to hit him, but if it goes on I think he might actually hit the boy.

So what should I do? How do I get him to stop, because nothing I've done has worked so far and it's like impossible to ignore him. Why won't he leave me alone?

I tried asking this question on yahoo answers, but no one will answer me and the one who did gave me an unusable answer so can you guys help me out?