I've had alot of experience with this, not that I was bullied but a classmate of mine. He was always the silent guy in the class and was always the target of paperplanes and all other things that are usable as a throwing object.
He always let people run over him and let him smack him and he never did anything back, also the teachers didn't do shit. But one day he got pissed at the biggest bullier of the class and he totally kicked his ass.
And by kicking his ass, I mean he hit him in the nuts and then he hit him in the face with his knee and eventually kicked him on the floor and punched him on the head a few times (like you see in the movies) then a teacher broke them up and he got punished, had to stay after schooltime and do work and stuff. But he earned some respect and they never bullied him again, just because he kicked the biggest bulliers ass..
So my advice is just to look for the biggest bullier of them all, and totally kick his ass. Even better is if he is bigger than you, this means you got more to hit

CAUTION: This may get you into alot of trouble at school, but you'll get the respect you deserve and eventually the trouble with school will be over and you'll get some friends.