Rotten Potatoes

Rotten potatoes smell nasty, like a big ol raunchy fart. Make sure a couple bags of potatoes grow mold, and then huck the smelly juice into the vents and in the bottom drawer of teacher's desk. Any extra can go in the trash can of every room.

Such a widespread attack of fart juice will annoy and confuse your superiors. They can't get rid of the smell because the fart juice is anywhere and everywhere. Especially the ceilings and carpets.

Then write in big letters on the lockers with white out:

BUM GOES OFF AT 12:30ish

Then at 12:30ish, you fart and say you found more potatoes.