Ignore them.....why do the eye for an eye thing..... Consider not coming down to their level.
If you want revenge, the best way is to show the person that they had no effect on your life or happiness. Revenge pranks just make things escalate.
That IS paying them back. It's the ultimate in having the last laugh. ;)
Get one of those stink bombs (If they sell them where you are that is) that you can step on and have it explode in their school bag, locker etc.
How about the classic kick me sign? Or steal they're phone and call random boy( if ur enemy is dude) and say that ur soo gaay fr them :D
Call their significant other on an untraceable cell phone and say " so&so is cheating on you" and then hang up. I read that in Dear Abbey a couple days ago and believe me, it does serious damage. Granted collateral damage is a side affect, if you can live with that then go for it. Otherwise call their parents and say " so&so is doing drugs" that would work too.
Write in their notebook/textbook something (I did it in pencil, no vandalism?). When the teacher isn't around get some chalk and smear it all over their belongings
ok if I was in middle school I would take my enemy and shove them in their locker and then I would take a pic of them in their locker and send the pic to every in the school HAHA :)