I use a black plastic mesh cup full of chaeto against the back wall of the tank. Enough light hits it that it seems to do the trick for me. I don't run skimmers or reactors due to the size of my tank. You can take a mesh bag like onions come in full of it and let it float for a while as well just to get the fight on. Ugly at first, but so is hair algae. Check nitrates, then do a big RO/DI water change if you can which I imagine is a giant PITA since it's a school tank. Nitrates may be zero due to all the hair algae though anyway.
Pull out as much as you can.
Emerald crabs are cool, but they can be little jerks too picking at polyps. Some won't touch the algae. Still, I love the look of them, makes the reef seem more real.
I'd suggest getting a few big turbo snails and letting them get to work. Cheap solution and easy to find.
You can try to go lights off in the tank for a few days to help them get a head start.