With regards to software compatibility on W7 I'm sure a lot of primary schools will use Photostory + Moive Maker 2.1 quite heavily for their photo / movie / animation needs due to their easy to use nature and the the fact they are free. Both are unavailable for W7. Photostory can be made to run with some effort after obtaining the 3.1 version. Also MM Live is available for W7 but is so cut down compared to 2.1
Useful 'if' laptops are Domained. Again like Si Staff laptops here are not domained and all docs are locally stored.
Way better offline files for teacher laptops
Again useful, but in the times I have had to use the W7s repair tools. they have not fixed the issue and have still gone the reimage route.
Much better self repair ability (system files, reg etc)
Again not a feature required by most pirmary schools. VLEs / MLEs are more than likely the route they will be going.
Way better over VPN/remote links due to a much faster network stack
But how much of that extra manageability is relevant to primary schools?
More managability via GP even if you only have a Windows 2000 server as DC
When in school Computers and on when in use and off when they are not they are switched off. Also from experience W7 has not given any increase in battery life on laptops.
Better power managment, suspend for powersave etc.
Humm as long as you research before you be there are plent;y of business grade machines that still support XP.
Easier install with support for non cretatious era hardware ie SATA drives
Automated multipass defragmentation
Fully integrated .net 3.5 framework and windows installer modules makeing .net stuff run faster and stuff install faster. This is important when pushing managed MSIs.
Nice fature but nothing that can't currently be achieved by Fn+Fx or a simple script and something like setres
Automated presentation mode that detects projectors when attached and offers a wizard to help
PCs come supplied the DVD player software and quicktime/xvid are free downloads, simple to include on an initial build.
Built in codecs for lots of different formats avoiding the need for DVD software or Quicktime/xvid etc
These are just my thoughts and as said above if buying new equipment with W7 installed then go for it, but I wouldn't rush to upgrade just for the sake of it.