I went to high school at a large suburban school, with 1,200 students in grades 10-12. Our school had one of those ghastly "auditeria," and I can testify from personal experience that they are sadly misnamed. The root of the word is the Latin audire, to hear, but hearing well was seldom possible.
Ours was a cavernous cafeteria with a raised stage in one corner. The floors were linoleum; the ceilings "acoustical" tile with hanging fluorescent light fixtures. It has those tacky accordion-pleated walls that could be closed around the stage to create a "little theater."
The stage itself was backed by the music classrooms, but there was no space to build or store scenery, or for storage of costumes and props. The classrooms and restrooms had to serve as dressing rooms.
Our entire school band did not actually fit on the stage, so when we had school concerts, they were on the floor, at the same level as the audience. Only the first two or three rows could see them. The seating was not raked, of course, so visibility was poor, even if the performers were on stage. With the linoleum and folding chairs, and just generally crummy acoustics, there was always a great deal of sound clutter.
Every time we had a school concert, assembly, school musical, or visiting performer the maintenance guys had to fold up all the cafeteria tables and put out hundreds of folding chairs. They had to reverse the process for the next school day, over and over again. I'm sure they loved it.
As a supporter of the performing arts, I beg you not to go this route. A compromise like this will never serve the community well. I can't imagine any local or visiting professionals wanting to use a space like that, and the students will always feel like they got "second best." They'll be right.