So my english teacher gave me the okay to set up an aquarium in our classroom. My friend has a 20 gallon high and stand he's bringing (24"x13"x17")

EQUIPMENT:
I'm going to get an Aquaclear 70 and mod it into a refugium. I have a koralia 1 and a koralia nano to use for flow.For lighting, I'm thinking about one of evil's PAR38 LED lamps, and raise it pretty high. Just easy LPS, and softies. I don't wanna do MH, too much evaporation. T5s are too expensive. I can do a PAR38 group buy and one for 99 bucks.

LIVESTOCK:
We'll have 2 clowns, and maybe a couple gobies or a blenny. A few LPS, frogspawn/torch/hammer probably. Some zoas, clove polyps, mushrooms. Green star polyps. Lots of macroalgae to help with the filtration. I'll feed pellets daily, minus weekend feedings.

Every one of the 30 kids is going to bring 5-10 bucks. So 150-250 bucks to play with.

Heres my equipment list:

20 Gallon High tank and stand: Free
Flow (K1 and K-Nano): Free
Heater: $20
Light: $100
Rock: $20(5-6 pounds of Dry, and some LR I have chillin in a bucket.)
Sand: $20 (20 lbs. Fiji Pink)
Filter: Aquaclear 70 (From Big Al's online): $20

I'll have a nitrate test kit to test water. That's it. Once a week water changes, daily top off when I get to class. Time in class and right after shouldn't be much of an issue.
Any recommendations? I'm trying to keep it simple.

I would add more Live Sand. I have a 10 reef with a Yellow Watchamn Goby and it doesn't look like there is enough sand for him to burrow in

I don't think we will get a burrowing goby. Too expensive w/ the pistol shrimp. Just enough to get by.

I need to add 10 pounds to my tank anyways, so maybe I'll just buy 40 pounds and use 30 in the classroom tank.

Automation would be important. An ATO (with properly researched failsafes) is very useful to avoid salinity swings. Also check to see what happens on the weekends (i.e. a/c shuts down, etc.). For a 20 High, I suggest getting an inexpensive T5 fixture (there are fixtures that cost the same or less than the par38). Something like an odyssea or fishneedit. Has evil said one par38 bulb would be sufficient for a 20 high?

IMO, if you want to save money, find used equipment. Aquaclears in particular are expensive since they aren't going to be used for actual filtration. You can have a successful tank without any external equipment. Don't buy "live" sand that comes in a bag; dry sand is just as good and cheaper.

LUCKY!!!