Hating sadistic teachers - yet impressed by Whiplash

First off I hate movies about mean and sadistic teachers - yes, there are some such teachers, and for the most part they are horrible teachers and horrible people and despite the romance of films (and books) about them the damage children rather than push them to achievement and greatness. That said, Whiplash, about a young jazz drummer aspirant in a school obviously meant to be Juilliard where a sadistic teacher pushes him to become a great jazz drummer, is compellingly watchable, dramatic, and quite credible. Essentially, it's a Black Swan meets Full Metal Jacket: a teacher who's much like a Marine Corps drill sergeant but in a performing-arts setting - obviously much more of a "guy" movie than Black Swan (though the young drummer has a lovely girlfriend whom he more or less abandons to pursue his obsession, there are no other female speaking roles in the movie - I would guess that's a pretty accurate picture of jazz aspirants). We learn a lot about the demands on students of jazz throughout the course of the movie, and even though the teacher's cruelty is far over the top it's quite possible that there are sadists like him at various top-level music schools. The movie is for the most part honest: instead of producing great proteges, he ruins lives and careers; however (spoilers here), it will not be a great surprise that the main character does finally show his chops with a knockout performance a jazz concert. Two elements I particularly admire: there's a significant ambiguity and openness at the end of the movie: was the sadistic teacher actually trying to destroy the student (who'd ratted the teacher anonymously and gotten him fired from the school), or did he know that by humiliating the student publicly he would drive him to one great performance? Was it all a scheme - or did a scheme go wrong? Second - a real surprise here - the hero did not end up with the girl. Even though he pushed her away, when he regains his equilibrium and calls her up, asking her to come to the big concert, she says coolly that she'll have to check with her boyfriend. Of course she would not sit around waiting for him for six months - her life has moved on, as it would in "real life" but seldom does in cinema. A powerful, thoughtful, provocative film that unearths new material in familiar territory.