Take a smoke bomb or an odor bomb to the bathrooms (if it is the teacher's bathroom, better), light it up and run your ass off.
Run naked (or in underwear) into the girl's bathroom while someone tapes it.
Throw eggs to the teacher's cars.
Write down on the school wall: Me and my girl had sex intercourse here last night, or graffitti the school.
Paint your hair purple or lime green.
Damn too many ideas!!!!!!!!!!!!!!!!!!!!