To be honest I don't agree with fish tanks in schools as the staff don't set a very good example to there pupils by letting fish suffer in dreadful conditions.
Also what do you do in the holdiays when the school closed.
That Holiday thing happened to -me- years ago. In my Junior High Biology classroom we had several beautiful tanks. They were partially built-in with built-in plumbing and everything. The niceest was about a 75G tank with a mature community population, large Angels and all. I think the teacher was good about caring for them (using the thinking of the hobby back then) and for a time I must have been her primary helper.
For some reason when summer holiday came she had no in-school care or place for the fish to go, something had changed from previous years I guess. I was the only hope for these fish since I had some tanks and had a 29G available (sounds sad now, doesn't it!)
I took them home and must have tried my best but back in those days, temperature matching was about the only thing anyone told me to worry about. There was certainly no such thing as common knowledge about cycling. The filters were small. I thought I was advanced because I replaced the plain fluourescent with a Gro-Lux red/blue light but of course there must have been way less than one watt per gallon, no co2, no added nutrients, so only the most hardy plants would live. At least the big angels and some of the others did well but I'm sure a lot of the fish were lost.
Funny, but virtually none of the Angelfish I see now, even large ones, seem anywhere near as pretty as those back in the late 1960's. They had very dark bold black vertical stripes against bright shimmering silver and often beautiful orange or red in the eyes and beautiful fins with trailing lines at the tips. Maybe I'm just very unlucky in what I see now but all the recent ones I've seen look nowhere near this healthy. (Sorry for rambling!)
Anyway, KatyKaye, I think its great what you are thinking of doing. Could be a nice learning opportunity for some of the students and you could do it with an eye toward the number you could successfully take in at the end of term, or that maybe a budding young hobbiest could take in at home.
~~waterdrop~~