Classromm hermits.

Hermit crab undoubtedly make great pets, and great educational tools.
In a properly set up environment, the children can watch them climb around, bathe in the pools, and see their colors change after every molt. The main things you need to worry about with classroom hermits is the temperature. I'm sure everyone remembers the frigid classrooms that they had to sit in for hours, freezing. The hermit crabs have to live in there 24/7! It's very important that you keep the tank warm enough. Multiple under tank heatsers, or an undertank heater, combined with a light will give you the nextra heat needed to keep the crabs comfortable. You don't want to everheat your tank either. So if you have a 10 gallon tank, then a 10 gallon and a 5 gallon under tank heater would work, or a 20 gallon heater mounted on the side. Mounting a heater with above the recommended wattage under a tank can cook your molters.
I am currently in the process of setting up a 10 gallon hermit crab tank for my biology class(That I am in, not that I teach) with 3 Purple pinchers, and i have an under tank heater, and a light.