I'm just sorry about how this discussion is likely to turn out with all the blah vs blah crap that floats around here. That's a tangent though.
FOSS in Schools is an idea I've considered many times. The points that keep coming back to mind go about like this:
Ideally, Students should learn tool categories, not tools. A student should learn how to use word processors not Word, Wordperfect or any other single branded tool. Heck, the branded tool I learned spreadsheets on is long since dead and I'm not that old. I use spreadsheets though, not "Excels".
This leads into the whole "schools have to teach what's actually being used in the work force. Market share. Market share. Windows is what they need to know." But a GUI interface is point and click. Unless you get picky your going to be looking at a plain old WIMP desktop. A different brand of WIMP desktop takes all of ten minutes to look over and understand. Windows WIMP GUI or any other brand.
Now, students also then get access to a variety of software and desktop. For the "computer lab" classes, it would be easy to setup computers with five or more desktops and if the user makes a mess of it; no worries, it's only the user account, delete the window managers config folder and you have a fresh start. Heck, build VMs and really let the students have a go at it. Maybe make the grade 13 computer class install Gentoo; one of it's development goals is education of the user.
That's all student benefits though which could include running Win32/64 software in a variety of ways under a *nix OS. There is the school to consider:
Most schools don't have a large budget to piss into computers so why not save the software fees and buy more hardware?
An LDAP network would be very secure for an environment where every geeks is trying to crack the network (it's what geeks do in highschool).
Even better is a setup one school used which had a server running remote desktops out to the workstation dumb terminals. They had old hardware they could continue to use while providing processing power and responsiveness from the server for multiple logins. Everything is kept secure on the server too so backup, recover and year end/start are easy to manage.
Schools are big targets for malware too so there is obvious benefits there with students getting around proxies when websites are banned.
The school admin who is usually the most technically savvy teacher when not in class spends less time fixing broken computers. Kids will still find ways to break them but the damage is more limited and easier to recover from.
Cost is an obvious one even with the education discount from MS.
Again, ideally the school should have Mac, MS and FOSS systems setup to promote learning rather than branding.
Now, schools tend to be very traditional and slow to change so there is a very conservative view towards considering something outside of what they are running now. There are politics between schools and school boards of course. There are all the other reasons you can think of. There are also the school that have used some FOSS and love it though.