While racks are great for humidity, they're only easy to maintain rack temps if the classroom temp is consistent. I find that classrooms fluctuate a lot. Especially at night and throughout different times of the year. You would have to change the thermostat settings constantly to regulate the correct temps. And that's only for the hot spot too. It doesn't really affect air temp unless the tubs are small. So a pvc cage or something similar would work much better for maintaining the temperature of a classroom.