so a few that i have heard happened at my old school and around:
1) drop 3000 bouncy balls onto the first floor from second during lunch hour
2) the whole grad class runs into the library/wherever and planks
3) water gun fight thru the school halls
4) sneak into school after custodians leave, sarran wrap and duct tape all the doors, vaseline all the door handles and locks, move the staff room furniture into the lobby, put a few hundred cups of water in front of every door
5) dissassemble, then reassemble a teacher's car somewhere in the school
Ski for Duffy.