How long have you had it set up at the school? If your parameters are all in check I would say you are good.
The system has been up and running since June 7th. My pH remains at 7.8 doesn't seem to want to move to 8, nitrites are 0, ammonia is pretty close to 0, and nitrates are about 30, but I have been doing small partial water changes to get that back down.
I would really love to get a Goby, Mandarin, and a star fish or two.
Thanks so much for your input.