This is the thermostat on the wall:
On the left is a heat strip telling us that the the temperature is 25 degrees Celsius. On the right is the thermostat. It's inside a locked plastic container in order that people in the room can't change its settings. The temperature it's displaying is 22 degrees Celsius.
I suspect that the heat detector is itself inside that plastic container, and is therefore unaffected by the actual room temperature. It wants to make the temperature 23 degrees, so it sets the air coming out of the fan in the roof be warm. However, as it's in its own heat-shielded container, it never gets to be 23 degrees so the heat keeps on coming.
The result is that the room is warmed up by 20 bodies and the heating system, so we're all feeling very uncomfortable.
Oh, and the plastic sheet contains advice on maintaining the temperature that is geared entirely for keeping the temperature warm ("remove clothing and towels from the radiators" — what radiators?). It is especially concerned that we don't open the windows, which would be more relevant if the windows were actually openable.
Only another nine teaching days in there to go...