What do ya do.

shit in a big and light it on fire at his door step, knock/ring or w/e and run
i dunno how funny this will be in real life, but i saw it in a movie once(im sure you all know which)

Show up at his house and stand above him while he is sleeping and wait for him to wake up with a big stick in youre hand.
Scare the shit out of him, if this fails and he trys some shit have some friends hold him down and put a rubber band around his balls, then he will be scared. That would be pretty sweet, but I can handle assult charges im not 18 yet so I get wiped in a few years.

Just walk by him prison style and stab him real quick with a stilleto. In all actually though doing anything about it is pretty stupid. The fact that your still IN school, well after you get out its like highschool was nothing. So unless you did something serious its all just dirt on your shoulder.