Also when talking about inexpensive compute device for education, We cannot ignore Chromebooks. Asus Chromebook C223 costs just $189 that's for device with 11.6" display, dual core CPU, 4GB RAM, 32GB storage+SD card, HD cam and WiFi5. RPi + similar accessories would cost more.
I think Google is subsidizing entry level Chromebooks.
Of course usefulness of ChromeOS itself or the privacy implications is debatable and sadly full UEFI firmware replacement for this particular device isn't possible but there are lots of other chromebooks where we can run Linux/Windows or to some extent even macOS like regular PC.
But in my experience[1] browsing experience on an entry level Chromebook is miles ahead of any ARM based SBC mainly due to hardware acceleration mess.
[1] https://abishekmuthian.com/reviewing-the-chromebook-google-s...