One of the big differences between an iPad (or any other tablet) and a Chromebook is that a Chromebook can easily be "locked down" and monitored so the kids won't be playing games on it when they're supposed to be doing their schoolwork. I'm guessing it
could be done with iPads and/or Android tablets, but I don't think it
has been done.
From the Chromebook's education page ...
Manage devices easily from the cloud
In the admin console, administrators have full control—enabling and disabling apps and software to all network devices.
Not only the above, but it can be easily used for multiple students (keeping costs down).
https://edu.google.com/products/chro...al_active=none