The girls lacrosse team enters the locker room through a door that the janitor had previously locked.
The locker room wouldn't have a wooden floor.
The janitor locks the locker room door, trapping Eric, Fez, and Hyde inside the locker room. The locker room door locks from the outside with a key, but from the inside, with a latch. They would not have been trapped in the locker room at all. Also, fire codes would not have allowed the locker room to be locked in such a way that someone could be trapped inside.