hmm well first off try and not get caught, lets see what could u do, u can super glue all the locks on the doors, so people cant get in, id use some model airplane epoxy, u mix the epocy and the resin together, hardens like cement, hahah that would never come off hehehehe
what about catching some squirels and saving them up and letting them go in the halls, and for an extra touch you can dump some oil on the buggers
find out where they keep the buses for ur school, get like 10 kids(trustworthy ones) and go and let the air outta some tires, dont slash them casue if they find out its u thats a shit load of money,
But one this is for sure, i gotta find one for myself, but when you do it, do it with trust worth people that wount tell a soal, cause one person tells another and before you know it, u get caught, u should do it for your own pleasure