I wouldn't expect a classroom temperature being able to drop that low. They wouldn't be able to get it warm enough for the students in the morning if dropped that low. Most schools I've ever been in, some very old, are probably in the 63-65F area. Maybe a tad lower during winter months. Being that your cage is 2' high, the RHP has to work extra hard to heat the lower portion of that cage. In a pvc enclosure, 80w of RHP is more than plenty to keep the entire thing warm if the ambient temps are 65 degrees.