Oh, and to answer the question, if you actually want to run your application directly on an iDevice (not web), I'm pretty sure you'll either need to Jailbreak it or get a $99/yr developer program account. In the mean time you can learn the programming side with the free Xcode toolset and run on the built-in simulator.
There is a
University program that will allow you to distribute on actual devices but I don't know if one can get it set up for high schools.