Wow man I have been out of school for a looooooong time, but I pulled a few good pranks in the past.
* fill the waste basket with water. Put a bunch of crumpled up paper balls on top, so they float, and stick on top of the rim. with any luck the teacher will "step" on it to crunch them down, and end up with a wet leg
* get all the kids with wrist watches to synchronize their watches, and set the alarms for the same time. An alternate is to stagger them, so they go off in succession, one at 1:15, another at 1:17, another at 1:19, another at 1:22....
* everybody stare out the window at the same time
* get one of those musical greeting cards, rip out the musical piece, and hide it in the classroom
* superglue the teachers edition (if a bully is bothering you, superglue the dial on his locker)
I got tons of them...
_________________
I drink, I smoke, I gamble, I chase girls-- but postal chess is one vice I don't have.
Ah, but is life worth living if you have to worry about so many things?
~Mikhail Tal~
World Chess Champion 1960-1961