This is closely aligned during the night janitor of the school do not know how many students were in the class to keep it locked classroom, thinking that no one then.
School maintenance worker is justification. Night close!! I don't know whether there are classes in the student's classroom to pedestrians whilst providing the log I think nobody.
Together, it is even janitors of the School against the night, and did not know that there are students studying in the room together, and went to log in classroom thought that no one would.