RISC OS is not an ideal server operating system, Unix, Novell and even windows are better options.
I think the way forward for any schools with RISC OS systems remaining, is citrix or terminal services. Citrix works very well on a strong arm risc pc, but is unfortunately limited to 256 colours and full screen. The new RDP client does not have these limitations.
We use citrix (no risc os though, apart from my own personal systems) and it has lots of benefits.