While in the room with all the lockers, open one of them with a girl's picture on it. Go against the locker door. Go nearly inside the locker and knock on the girls leg. She will now have an exclamation point above her, and there will be a clearing or an alert mode in play; just quickly go into the locker and crouch. You can knock on her leg about six times in a row and the guards will be confused for awhile.