iOS 6 is soon to be released and with it comes some great new accessibility. A few key features is the ability to lock the home button, turn on and off the touch (so students cannot leave an app) and turning off the motion.
See the link below for more information on iOS 6:
http://www.apple.com/ios/whats-new/#accessibility
See the link below for more information on iOS 6:
http://www.apple.com/ios/whats-new/#accessibility