The Children's Online Privacy Act (COPA) has been a big road block to schools using iOS devices with students under 13. It's really just easier to send you to the Wikipedia page to learn why, but I'll give you the TL;DR version. from Wikipedia:
So this basically means that its nearly impossible to deploy iCloud and iTunes U to kids under the age of 13. Apple has published this page to explain the ways that iOS 7 is making it easier deploy iPads in education. Near the bottom, there is this tidbit:
This is a very big deal. While we don't have all the details, I am thrilled that Apple has solved this problem.