How to get this guy off my back?

Urghhh.... so there's this guy in my math class who has been really bugging me lately, I'm a freshman he's a sophomore and he has recently been bugging me about Sadie's, like pretending to like me and asking me about 50 times each class to go to the freaking dance with him. He's definately joking, and is being an a** about it, and I don't understand why he is doing this because I'm def not a weirdo or ugly or anything(although I can be shy). When he bugs me, I tend to just stare at him or ignore him, because I'm trying to concentrate in geometry lately(grades slipping) so I don't have ANY time to deal with his stupidity. Anyway, what I want to know are some ways to get rid of this a**hole and get on with my life. No elaborate schemes or anything, and don't say ';Stand up for yourself'; because it's impossible to do, as the only time I see him is during mathematics, and he sits next to me but the teacher can hear EVERYTHING!(except, strangely enough, said enemy)How to get this guy off my back?
say ';ahem. can you please get off my back?';How to get this guy off my back?
Tell him youll go with him. Then show him up. Make him look like a doof
report him to your teacher tell her/him that you feel hes causing your grades to slip!
Ask him if you say yes will he shut up? Then don't show, or do, what ever.
You're doing the right thing then. I'd just stare blankly at him till he went away if you don't want to say anything. Probably the ';Are you quite done wasting my time'; look would also be good lol. Or just walk off on him if he gets too bad.
Turn and look him straight in the eye and say, ';Knock it off.'; It doesn't matter if the teacher hears. If she makes a big deal of it, tell her that you are tired of being harassed by this person. That should end it once and for all.
Tell him to get lost!!! If you don't like him, or he annoys you just sit somewhere else in class or tell him he's bein a real jerk off and to stop.

If he has any smartness in his brain he should leave you alone but if he doesn't then try to ignore him as much as possible or ask your parents or teacher for advice.
When you say he's joking, do you mean he's doing it to make fun of you? If that's how you feel, I would ask the teacher after class if your seat could be changed and say you feel like the guy is poking fun at you and it makes you uncomfortable and, most important, distracting you from something you want to be on top of (the class and your grade). If the teacher refuses, go to a school counselor and complain.