I'm happy your seahorses haven't had any run-ins with the hammer and frogspawn, but that doesn't mean it should be recommended. I kept seahorses for a couple years and let me tell you, there's nothing worse then seeing a horse killed by a coral. I learned the hard way. Its simply too risky, and while some have success, i say, stay away. The seahorses will be the stars of the tank, and since this is for a school, avoid any potential problems and play it safe.
Sam, PLEASE do not add the Torch coral especially. There are so many other beautiful and horse friendly coral. Including macro algae which looks fantastic in horse tanks. ( I just got 4 neat species, but there just little frags now, when they've grown out, I'd be happy to donate some for the horsies hitching posts!)
Also, you MAY be able to find someone willing to donate, or cut you a great deal on the horses. A lot of aquarists have so much luck raising H. ERECTUS, that they really have to give them away (I got 4 gorgeous 4" yellow and pink erectus from a hobbyist who simply coudn't get rid of them for just a few coral i traded.) If you post something on seahorse.org you *might* get lucky. (there is a online website SEAHORSE.ORG which is a WEALTH of information on seahorses, in case anyone didn't already know that
Here's a pic of my now dismantled 46 gallon bowfront reef seahorse tank. There's 4 ponies in there you might see if you look hard. Just to give you an idea of all the coral that can be kept with seahorses, without endangering them.