Most public school teachers I've interacted with are apathetic powerless bureaucrats. My experience in private school is different. We had corporal punishment and other severe punishments there, and teachers actually had control of their classrooms and could teach effectively.
My point isn't that teachers are to blame. I understand that the issue is systemic and requires support of the school, parents, and teachers. I just disagree that controlling the classroom is "yet another thing" for a teacher to worry about, when it is literally priority #1.