There are a few things I would do. I'm crap at problem solving though. lol.
My first course of action would to be ignore him. Not in the "I can't hear you, lalalala!" way, in the "You don't exist on planet Earth" kind of way. If he starts making jokes and doin that mean, stupid crap - just talk straight through it. But it kinda sounds like you've been trying that. Soooooo,
Step 2. Tell him to quit. If he doesn't the first time, really tell him to quit. If he persists, inform him that he's an idiot and say something along the lines of "You stink, have you heard of soap?" That /should/ embarrass him enough to make him quit.
Step 3, worse case-scenario, inform your parent(s) that he's a jerk and they you're absolutely gunna deck him. Then do it. ^-^
The third step is kinda a joke. lol Like I said, I'm not very good at that. But I try. =)