At least with a Chromebook, there is a gate that you can open if you want. The Crouton project allows anyone to install a full OS. The best part is that if it gets broken, there is no danger or punishment. Just reset and everything is back to default and your files come back. Get good at it and then it is probably time for a real computer...
Initially our school district planned iPads, but backtracked over cost. We were initially excited for them, so that our kids wouldn't have to carry so many heavy textbooks. But the quality of the textbooks on the Chromebook are terrible. It's as if the publishers simply took galley proofs and dumped them into a pdf.
Would you expect the textbooks to be better quality on the iPads vs on the Chromebooks? Why?
Back when I was in school, I was getting some of the textbooks second hand from the year older students and selling mine to the younger ones, on a fair organized by the school.
That being said you have to understand what chromeOS is and isn't.
Some schools also avoid Apple and instead use recycled/repurposed computers that can run as a Linux or Windows thin client.
Edit: wording
In our case we were 3 weeks at sea with only email access.