Migarate e-mail to google apps or @edu as this cost nothing.
Plan the money
Look at upgrading your internet connection
Virtualize the servers go for switch SAS storage.
New network Juniper stuff looks good with stacking.
Use VDI desktops and thin clients and show how much electricity can be save ask it that can go towards IT?
If you got the money go for it people! :D
If I was to replace the entire network, this is what to replace.
At-9816GB Fibre switch
1x 3com 2948
1 x AT8326GB
10 x At-8350GB
can I also wade into the discussion and sit in the ' upgrade the infrastructure, worry about the servers later' camp, with a +1 for the HP Procurve kit. With a particular +1 to the 5400zl (but check your SD cards folks!)
I can get Juniper switches "cheap" if any one wants to go through me as I'm a Juniper partner, the Juniper EX2200 switch is awesome!! I think it's around about the £700 mark.
If anyone wants needs servers we are partners for IBM and Oracle, and partners for Juniper so anybody needs anything let me know.
+1 here for ProCurve
Also consider what you could do to divide you physical space up between you and the servers i.e. could a partition wall be install in you office space. My personnel view it should be possible to run all schools in 42u of rack space.