1st, what Joe said.
You could try Masked gobies (Coryphopterus personatus.) I have three in my tank. They hang out together, sort of, so could be considered schooling fish in a manner of speaking. They are full grown at 1.5", though, so you take your chances w/ larger fish, obviously.
Anthias have special care requirements. Not the easiest critters to keep, and IMO a 75 is too small for a school.
I wouldn't attempt to group tangs in a home aquarium, personally. I can't imagine trying to keep 5-7 yellows in anything less than a few thousand gallons. (Exceptions to every rule, and someone will chime in that's done it, but I wouldn't.)
Assessors? Nice fish. Haven't run across one yet that I could afford, let alone several...
One tends to think of schooling fish as not being territorial. That's in the ocean though. Confine them, and you'll see how territorial they can become.
You could always try Moorish Idols. (Before someone gets on me - I'm kidding!)