thanks. I thought of Chromebooks too. It may be an option. That you need a Google account to boot USB is very understandable;-)

BTW: I just found this (when looking for open hardware and remembering the OLPC X0 I bought and sponsored ages ago):

https://www.indiegogo.com/projects/infinity-a-computer-anyone-can-build-and-explore#/ , http://www.one-education.org/

Regards

Peter