What I've long suspected turns out to be true; you can spend less money on hardware as well when using open source software. Double the savings! Don't believe me? The IT manager at Westall Secondary College (where I occasionally help out) has said just that in an article called "Ubuntu breathes new life into school's abandoned hardware".
Because we get a plug, I suppose I should explain a bit about the work I've done at the school :-)
It's important for a school network that if authentication is required, a user's login will work on any system. With NetWare, this was the case on the windows workstations already. Linux needed a bit of convincing, but with the right pam-ldap, nss-ldap and pam-mount configurations, all users can log into Linux as well and access their personal shared drive space.
With Zimbra as mail solution, a small amount of configuration changes means the same authentication system can also be used for email.
Still on the horizon are some MythTV tweaks (Do other schools still have VCRs? How quaint!) and a nagios setup, so everything is easily monitored.