Follow-Up:
A great HS prank also has to do with stairwells. Go to a local pet store and stock up on crickets. In between periods while students are scurrying to their classes, go to the top of a heavily traveled staircase. Release those critters all over those ascending the stairs. I did this prank in the early 90's when big hair was popular. It was better that way. it was hilarious watching the hairsprayed guidettes scream as the crickets burrowed into their lovely big hair.