...we need computing platforms that are restricted in the use of the computer, to make it function better as an educational platform.
Cheap Chromebooks the sim card explicitly removed and without the wifi password used to fill that niche, but now most new Chromebooks are touch-enabled and they'll be able to run Android soon. In other words, Google is about to mess it all up for parents.
And it won't be long until one kid figures out how he can download an apk to a usb stick or a memory card, and can play it on a friend's Chromebook. By the time 5th period rolls around, everyone in his school will have seen it done. And within a week or two, all kids who use Chromebooks in the entire United States will have seen it done (even if they themselves do not have direct internet access).
At that point, parents will just have resell their Chromebooks on Ebay and trade them in, for either paper notepads or old-fashioned electric type-writers. Or they'll be forced to just place the Chromebooks under lock and key like they've been forced to do with the wifi hub, the router, and everything else.