It is also popular in some parts of Scandinavia.
Why you ask?
As a school teacher I can see
- for ages no proper trained IT staff in schools
- I know better linux, rpi than them. Heck they read IT news from cnet.com
- managing+ security in local servers is very difficult
- money for space
- google edu is/was almost free
- HIPAA equivalent rules
- though everyone will talk and tell linux, libreoffice
- the polishing and consistency of chromeos is great (for cheap $150 laptop)
- ideally linux foundation or some one should have made a 'school appliance' but ...