It's not really easy depending on who you ask and running Crouton isn't really making it a linux box in this way as you're just running on top of ChromeOS with most of the hardware integration still handled by ChromeOS.

No school would endorse this because I'm sure crouton isn't in their support package. Doing it 'right' often implies opening the case, voiding your warranty, removing the write-protect screw, flashing away ChromeOS with a third party build of SeaBios, installing an unsupported Linux OS on the hardware and praying drivers exist in the mainline kernel for your device, then making due without any of the ChromeOS cloud-goodies your device was given from Google. Not really SOP for organizations buying in bulk with warranties.

I do it because I like small, cheap computers running Linux well and thankfully ChromeOS is Linux-y, but for most people, this is still very locked down. Even being able to unlock ChromeOS devices is probably more a side-effect than a willful desire from Google to be open.