For use at high school level, I would imagine that you would want to build a special distribution anyway. One that for example already includes packages, such as Gloss, that would be useful in teaching children programming in Haskell without they having to go through learning to use cabal (which is a bigger hurdle than installing Xcode IMHO).

But I wonder, would those students not use school equipment (which supposedly would have all software pre-installed)? Do they bring their own Macs? (I'd be surprised to find a whole class of 6th graders all owning Macs...)

As a further data point, yesterday one of my colleagues gave his 17-yr-old daughter a copy of the "Learn you a Haskell for Great Good" book. She started to read it, and wanted to play with Haskell on her MacBook Air. First step, download ghc. Discover that it will not install on Leopard. Step two: upgrade the operating system to Snow Leopard. One hour later, attempt to install ghc again. Discover that it requires XCode. Step three: buy XCode from the mac App Store, and wait two hours for the 4Gb download over a hotel wifi connection Step four: hotel wifi access runs out before the download is complete, so give up and go back to watching the movie she downloaded earlier, but has not been able to watch whilst all this downloading and upgrading has been happening.