I really enjoyed this film because, as a teacher, I recognized archetypes and situations and felt that the writers had a good sense of the craziness that is teaching in high school. However, I found that the political issues surrounding public vs. private/independent vs. charter are glossed over and dealt with in a single scene, yet they expect intellectual investment from the audience without true discussion.
I also saw a serious rift between two separate aspects in the film. Thee is a serious plot, and a serious subplot. Questions of unions and stakeholders, finances and resources are all there. And, yes, there is a little bit of humor in there. But then there are the supporting characters, the other teachers who are so criminally negligent and ridiculous in what they do that it undercuts any realism in the major story arc. Yes, in a school some teachers are eccentric and if this mockumentary wants to show a teacher singing a silly song in class in an effort to increase scores, then that's great. But then, to show a teacher making students cry repeatedly, or counselors endorsing alcohol and drugs? That makes for a great moment in a complete parody, but not in a film which purports to show the serious side of things.
This film owes much to the Christopher Guest/Harry Shearer/Michael McKean/Rob Reiner school of films. The dry, low key humor and scenes that are just a touch awkward (one character actually references Spinal Tap). But then it also tries to be the movie "Teachers" (Nick Nolte) with its hard moral choices and complex central character and also "Police Academy" with its wacky and zany supporting players.
The good parts were great, the dumb parts were silly, but the movie was not a cohesive whole.