Microsoft already runs a program similar to this called the MSDN Academic Alliance. It's geared more toward college-level computer science-related departments than K-12 teachers, but it does include a lot more software. For a relatively low price ($799), Microsoft essentially gives the department a volume license to the entire MSDN package (pretty much every Microsoft product except Office). At my school, I know they waived the $799 fee and just gave MSDNAA to us. They also allow the department to give the software out to their students for free, which is a nice benefit. The program is obviously geared toward getting CS students programming in and using Microsoft products, but hey, it's cheap and I certainly won'to turn down free software.

Granted, Microsoft's program isn't as broad or open as Apple's, but it certainly is worth noting.