In the city of Kyrthar Tahlketh, sealed for a thousand years and ruled by the two factions of demons and devils, there is a small enclave of survivors, protected by the city’s ancient magical defences, who live in their small sanctuary. They cannot really leave it without risking being caught by the devils, demons and other dangers of the city, so they have to develop strict social rules with harsh punishments. And they also need to teach these rules to the new generation in order to survive. Hence is a classroom.
You must obey the rules or there will be corporate punishment and in the worst case … banishment.