Academic Festival Overture - boy, does that ever bring back the memories. Back when I was a young sprout (but after my military time), I attended Washington University ("in Saint Louis", as the sports folks always say).
Although I never took a music course while enrolled there, I played both in all of the shows (including three in their just constructed, spectacular, 'all of the outlets in the orchestra pit worked', state of the art theater) as well as with the university's orchestra, in the usual bass clarinet, extra clarinet, "Can you handle the contra-bassoon part on Beethoven's Ninth?" duty.
(At the same time, I was also doing shows at one of the local community colleges and playing commercial stuff. I was one busy little beaver, I tells ya...)
One thing that was played by the orchestra for every graduation at Washington U (at least while I was there) was Academic Festival Overture. Although rehearsing it got kind of old, I always liked the part where it rounded off into "Guadiamus igiture". To this day, when I hear that in a recording, it brings back goosebumps.
Good old Wash. U. was the school with the two bassett horns (one of which was minus a neck and the massive old Heckel straight contra-bassoon. They were wealthy enough to afford just about anything, although I never eyeballed their saxophone collection - everyone that played there brought their own.
They didn't have a single decent bass clarinet out of the five or so in the instrument room, though...
Only the director knows the instrumentation, balance, strengths and weaknesses of each section to pick the "right" pieces for the current group. My mentor taught me that a concert or festival is a setting to show what your band can play---not what it can't. A wonderful resource that wasn't available when I first started teaching band in 1970 is Smart Music. It costs only about $40 per year and literally has hundreds of band pieces in all different levels of difficulty. One can listen to a professional recording of each work and follow one of the band parts. I like to follow the 1st trumpet and 1st clarinet parts to gauge the demands upon the brass and the woodwinds. An added bonus when you pick one of these pieces to perform is that your students who subscribe to Smart Music can play along with the recording at any tempo and develop their pitch, tone quality, style, and phrasing as well as work on the technique required to play their parts.
Another excellent resource is the set of CD recordings of new literature put out by Pepper Music. (I think they still do that.) I used to play those non-stop in the background as I organized the band room at the beginning or end of the year, and 3 or 4 pieces would reach out and grab me that I would give a second or third listen to. I found early on in my teaching that if I didn't love a given piece of music, I couldn't fake it and inspire my students to enjoy working on it. I think most directors develop a fondness for the styles of certain composers and watch for their new works to be released. I also feel strongly that programming should include some of the standard works for band that have stood the test of time as well as the "new" literature. Today's students need the opportunity to be exposed to the "classics" just as those of us in the earlier generations were. Good luck with your quest.
I recommend to all Jay Bocook's Sacred Harp. We just performed this with our ensemble this spring, and I was terrifically impressed with his evocation of sounds I heard coming out of little churches in Alabama back in my youth. Probably a solid grade 5 difficulty. That's just in my estimation, but it's hard for me to tell any more. It really helps if you have really fine soloists, and we do. Here's our performance - please enjoy and tell your conductors...