This little article shows how to limit what kids can use on an iPad for any given lesson. It can stop them from even seeing their home page so they cannot launch anything but the app(s) you have planned for them. Cool and helpful.
I tried this social networking bulletin board to have my choir kids listen and critique their festival performances. It went fairly well. The only thing I'd love to find is a way to have them post their idea without seeing what others have written. It's hard for a teacher to know how much of what they write is simply restatement of what others have already written once it gets rolling.