I'm not a leader but have worked in ICT departments in UK schools for over 10 years so will give my 2p worth.
I think its a great idea and will save money but the idea would work best if you used the PIs as thin clients that connect to a Windows 2008 Terminal Server, Debian has Rdesktop so getting a script koncked up that loads that after startup or reboot will not be a big issue. There may be slight issues with needing a startup script to set the time on Debian before starting Rdesktop but once more, not a big thing.
I'm guessing your school uses Sims as its MIS system, this means all Sims users need MS Office, as registers are now done on in Sims, all form/tutor rooms need atleast one computer with this on. So your stuck with MSOffice unless you want to only license it for those machines but once retraining staff, changing lesson plans etc are taken into account its probably easier to stick with MS Office, you would also avoid any backlash from staff.
You also have to accept that thin clients are not really suitable for media work so only suitable for classrooms that are not booked by media departments, check with your time table manager.
So if you accept that the best way to proceed without a staff backlash and keeping software issues to a minimium is to use the PIs as thin clients that connect to a Windows 2008 server then you need servers that will serve your project well. Any servers you buy must have lots of ram but ram is expensive especially if you go for the larger size sticks such 2x8gb instead of 4x4gb. Don't worry too much about storage space as these are just for your terminal servers but some form of raid is required as if one TS server goes down even if you have others the clients can connect too its still puts the others servers under more strain.
I would say you need a minimium of 3 16GB ram servers, all with 3-5 year onsite warranty, so you need to add that to your shopping list. Your network infrastructure will need to be not super expensive but atleast new and under warranty and not bottlenecked, each classroom should have its own switch, either a smart or managed switch to avoid one loopback taking down all the clients, ideally with a uplink of 1GB to the core switch that the servers connect to.
You now need to install Windows 2008 server on your new servers, use server manager to ensure its configured as a terminal services server, then install all your curriculum software onto it. To keep it simple for now don't bother with load balacing as you just want to test the system out, connect using rdp to one of the TS servers using a xp machine, once logged on test all software.
You now need to configure the Pis to bootup and connect to the TS server, as the PI is designed to use Debian, its probably easier to stick with that to avoid hardware issues, configure it to autologin with a basic account and then launch rdesktop.
Opinions on what specs you need will vary but its a great idea that will save money, I would love to see schools using open source in the Uk more but getting the science, DT software such as birchfield etc to run on Linux is a pain but I don't want to mention that as it will send your thread off topic again.
I hope you go for it but expect some issues but all of them are easily resolved if you remain positive.
Your IT staff should be able to do this, IT support people support and install the systems you choose and have selected, even if it means learning something new, I say this as a IT support person, there is nothing in your plan that will not work, you could even save more money by buying second hand TFT monitors and fixing the PIs to the base, how far do you want to go with this.
I totally get the idea about invigorating the teaching of proper computing in schools and I am right behind that, but as a UK school leader, I have an even more pressing problem.
I have three IT rooms in a secondary school with 90 computers running MS Windows/Office which are all so slow they are unusable and with very old and failing monitors as well. I also have virtually no money to replace them thanks to bad financial planning by a previous regime.
What would it cost to replace them?
90 PCs x £400 inc licences & monitors = £36,000
The cost of 3 year"s electricity with a PC power supply of 0.3kW and a monitor of 0.15kW on for 8 hours per day for 200 days per year @ 10p per unit
= 90 * 0.45 * 8 * 200 * 3 * 10p = £19,440
That"s a three year cost of over £55,000 (I"m assuming a three year replacement cycle here). We don"t have the money. I could lease, yada yada yada, but we"re on our uppers. Really.
If I could get RasPis instead, it would be a lot cheaper
90 RasPis * £22 = £1,980
90 new hard glass monitors @ £85 = £7,650
90 microUSB power supplies @ £5 = £450
90 HDMI to DVI-D converters @ £5 = £450
90 miniHDMI to HDMI cables @£5 = £450
and at a power rating of 0.005kW for the RasPi and 0.05kW for the monitor, three years electricity is
= 90 * 0.055 * 8 * 200 * 3 * 10p = £2,376 (Big reduction!)
Total cost is £13,356
I can afford that much.
My only problem is that our desktop is Windows and all our tech expertise is Windows. We could move our storage to the cloud but we would need to authenticate logins against a Windows Server active directory.
The financial case seems very strong to me.
It wouldn"t be nice for teachers who all have their fave educational program that only runs on Windows, but these labs are almost exclusively used for web browsing, word processing, powerpoint making and occasional spreadsheets. Any other school leaders seduced by the idea?