I am a teacher at a secondary school (11-16 years) in England and our network is 100% Win98. From my experience MS is the preferred choice of OS for education. Some schools use NT, some use Win9x, but anything else is rare.
We used to have some Apple Macs, but they have been "retired" and replaced with PCs - "too expensive to buy Macs", "too difficult to nintegrate into our network". The SysAdmin is a 20 something who has no experience of anything except MS, and no inclination to learn anything else.
There was a tradition of using a whole range of machines and OSes because they would do the job best, but that has disappeared in the past 6 or 7 years. I have worked in schools that used BBCs, Acorn, Apple, Amiga and Atari's in different departments. No chance of networking them, but it wasn't necessary in the days before widespread internet access was available.
Art & Design used Amigas for graphics, Music used Atari ST with built in MIDI, Acorn was a big player in the educational software market. Now MS have come to dominate here as elsewhere. To many people there does not *appear* to be any alternative.
On a related note, I don't know what sort of deal MS offer schools, but I paid
