Dress up in real full plate armor with a nerf sword and start beating the principle, shouting, "BEGONE FOUL MISTRESS OF EVIL!!!", and "HAVE AT THEE, FOUL DEMON!!"
Ride a horse down the hallway that spans the length of the building.
Walk in wearing a full police officer's uniform and announce you're the new SRO.
Wear a ski mask and threaten to have your "Friends", pay a visit with their "Lead Sprayers."
Hack the school projector computer during an assembly so that it shows nothing but someone hitting Hilary Clinton with a baseball bat.
Remember the health diagrams? Photoshop your health teacher on them.
Show the office staff a "Full Moon."
Come to school wearing nothing but a werewolf costume for the rest of the year after Halloween.
Threaten to bring a pineapple to school.(the classic grenade.)
Ask the shop teacher how to make a pipe boom.
Threaten to send a package that would be, "An EOD delight"
More to come.