I've heard of a few: Two schools have a huge rivalry, but the buildings are basically carbon copies of one another, so some people switch the giant light up signs out in front of the schools.
Another one, that was apparently caught on camera, was a camper(s) pulls into the parking lot and disgorges the senior class and they TP everything in sight. Total time elapsed? About 2-3 minutes. It supposedly looked like a Navy SEAL raid.
Some background on the next one- our neighboring school's mascot is a cardinal and the mastermind's (my Junior High science teacher) father was his principal or superintendent (don't remember which)
Anyways they spray painted a bunch of chickens red, and released them during the weekend so that they weren't found until the next week.
Our class has decided to revive one that my friend's Dad did.
Make a harness that fits under your clothes and attaches to a rope, then learn how to tie a noose. (See where I'm going?)
We probably won't end up doing it but it would be a surprise (read: traumatizing) if you came to school and found someone hanging in front of the doors.