Careful with kids and the Aquapod stand! It is top heavy!
Especially the 24 gallon. The 12 as well, IMO.
That's just my opinion from a very non-professional engineering standpoint. I've sold these before, and talked many out of it, and I just don't trust the stand. In a classroom, with peering eyes of kids and hands on the glass, I think this is one you should steer clear of, unless you fashion your own solid stand.
And please don't think corals are easier than fish. If anything, they are tougher. There are corals that are extremely hardy, but the same goes for fish.
I put together a 12 gallon Aquapod at my LFS where I work, and it has 1 six line wrasse and 1 pygmy geometric hawk along with a cleaner shrimp and some brittle starfish. All the tank has is 10 lbs of live rock, and 1 bag of CaribSea's Arag-Alive sand. We feed them once every other day with about a 1/3 cube of frozen mysis, and leave the lights on for ~8 hours a day. We also chose simple corals to accompany them: multiple Florida ricordea, a devil's finger leather, a green favia, some mushrooms and zoanthids, and a toadstool leather frag. Occaisionally I dose Lugol's concentrated iodine solution (barely 1 drop) once or twice a month. We've only topped off with RO water over the course of the last 5 months, and that's it. No water changes. Not even feeding the corals. Just clean the glass once a week and feed the fish several times a week. You could opt to do even hardier fish and feed them 2 times a week - damsels are resilient fish! Total cost was about $800-900 including everything. But enough about that. I know that near $1000 is probably what you don't want to spend.
For a teachers budget, the free stand sounds nice in the first link of the Nano Cube, but I do not like the quality of this product. I think the overall quality of the Aquapod is much more solid. I guess it's the better plastic. Their setup is pretty easy and overall, I think you'll be most happy with that. It's just that stand I can't get past.
I would say the first link with the 12 gallon Nano Cube Deluxe with the free stand is your best bet for the money. Though I would spend the extra $50 and steer clear of JBJ. But with 10 lbs of live rock and ~20 lbs of live sand, you should be under $300 (with the JBJ) no problem, unless someone is trying to rob you blind.
