At BooHoo4U, re covers.
You want to take a device that's priced at "only" ~$200 for educational use, costs another ~$75 if you want to add that vaunted pencil, and then slap on another ~$100 for a child resistant case? That's a pretty expensive bit of kit you want to foist upon a school that may already be strapped for cash.
I don't know about you but the school where my son teaches could better put that kind of money into other frivolous things like actual pencils, paper, lesson books, or providing a nutricious breakfast for the children.
So which do you choose: a fancy Apple device that others have shown to be a maintenence nightmare that will require even more money to keep working, or to give them the base tools with which the students can Get Shit Done?