One for your music department - Guitar Pro Free for Education
I came across this as I was just about to confirm costs to buy the new version for our Music department as they have an older version and enjoy using it but needed a newer one (preferably one that complains less in french as no-one in the team speaks or reads it!) as well as more licenses due to more hardware and came across the fact its now free for education!
Guitar Pro 6 Education Program
If you go to that link and sign up, it ask for a "purchase order" but as you see from the example its just a letter headed paper "order" so I am sure that will be easy to obtain, takes about 48hrs to get verified and sorted but you get the software for all platforms and the extra sound-sets as well (over 1Gb worth of them) so well worth doing.
I have not deployed it yet so cannot comment on how well it behaves on your network so please don't shout at me for it, but certainly worth looking at for your school, oh and even nicer you can get it so students of yours can get discount on purchasing it for home as well :)