I'd try to have a small boot server in each school. That would get your thin clients booted. Then, you could have centrally located application servers if you want.
SkoleLinux which means "SchoolLinux" is gaining poularity, yes. But as far as I know only single schools have started to use it as of now, but many schools use it with great success. I now work at city hall in a town in Norway as a part of the IT-staff. We have decided to roll out Linux on all our schools.
What about SkoleLinux, I know that is gaining popularity in schools in Norway.