If the goal is to teach children how to use computers for the future wouldn't
it be better to use both Linux and Windows? I have done consultations at a
few different schools some are using SafeDesk which is a thin client Linux setup.
They seem to learn quite a lot from using both types of systems. Linux is not
going anywhere for quite some time. Set up the old boxes that won't run XP with
Linux, and upgrade everything else to XP. Give them the best of both worlds.