That looks good to me as a stand alone system that monitors the GFCI receptacle. I have seen GFCI trip randomly for no reason I could find, but sometimes it is caused by a tiny amount of intermittent leakage to ground in the load. I bet the school doesn't have funds to pony up the cost, or the powers won't think it is worth the cost. There are good reasons not to use GFCI receptacles for essential equipment. In my experience, GFCI circuit breakers are a little less prone to tripping, especially if dedicated to one feed. I would never plug my refrigerator or freezer into one, but school aquarium systems are a different story.
Another thought: the UPS could be re-worked with a large deep cycle 12 volt battery and trickle charger. That would give you about 10 to 15 times the run time of a standard UPS, and still preserve the switching and alarms of the UPS.
Good luck.
