At one high school the seniors scaled the school building and entered via the roof access where they proceeded to remove all the light bulbs in the entire facility. They neatly packaged the light bulbs and labeled them as to where they were taken from and stored them all in a very "safe" place. Then they wrote a scavenger hunt for administrators to use to find out where the light bulbs were located. Doing the scavenger hunt took almost an hour.
A group of senior girls gained access to the principal's office and covered everything--literally everything--with tinfoil. This included every single pencil.
This year at a high school where the principal wants to know about pranks that are planned so he can give approval or help the seniors think of a prank that while still funny, won't harm anything or anyone. Well, this year the seniors called him to let him know--that they were in the midst of hanging old tires all over campus.