At the school where I work there's a long standing tradition that seniors have a "Prank Day." One year teachers arrived at school to find a full classroom set up on the roof of the gym. (It had a flat roof.). This year my office was the target.
Toilet paper and plastic wrap....."the best $12 investment I ever made" according to one of them. Hmmmm, I think she might have been in the Principal's office enough times to get really familiar with the layout. :)