I made a VBScript file that opens notepad and tell you it's deleting files and it's a virus. I proceeded to copy this file into the shares of all the teachers. One student opened it with a teacher's computer, during a powerpoint presentation, and somehow it deleted a system config file.
The teacher didn't report me to the office, or even get mad. I avoided a lot of trouble on this one. I'm not sure how the head of the tech department will react when I see him tomorrow.