from my perspective, the music room will be beside or near the classrooms I guess so you need to soundproof it. We have guys here who are experts with that matter. About the music related stuff, I suggest combo amps. around 50watts, to save space. For mixers, 8 channel mixers will do also, but if this stuff will also be used to set up a stage, 24 channel might do the work even mic'd amps.
If your asking what brand to get, gear heads will answer your question.
don't mind me, I'm just an undergraduate Archi guy.
Peeves is online you can ask him about the drum kit.