And what happens during the 15 min that the teacher is OUT of the classroom, frogmarching, if that's what happens while he is still IN there?!?
I think the mere fact they knew he could do that kept them from acting too outrageous. Also he had lower hall duty which meant his classroom was near the principals office. It also meant that in effect he was the school bouncer. This duty involved stopping as many as 3 trouble makers from invading the school.