One of our schools have 150 Chromebooks (Toshiba) and work really well, the computer science department have just started using Codio for Python and SQL, the kids and teachers love it. They are also used as thin clients that connects to Citrix XenApp servers, this used to be the preferred option for teachers, but now they use them just as a Chromebook due to the speed and the ability to mark work online.
Another School is O365, they have just setup a GAFE account and have purchased some Chromebooks, they don't bother with SSO, both office and Google passwords are set the same. If they forget their email password, IT Support just charge both. I believe you could setup ADFS as a single sign on option, but as Sylv3r says, RM Unify works well and isn't that costly.