When I was in Germany this summer, the seniors have a "Lock Out" day where they steal the keys to the school either the night before or in the wee hours of the morning and then barricade the school off, sheets over the fences with slogans and everything. They'll leave only one entrance, and fill it with hazards. When people come to school for class, they won't be able to get in. To get the keys back, different staff members had to do what the seniors asked. Sing a song, do something stupid, etc. Everybody ends up getting the day off.
