They come from within a culture expressly for the purpose of reproducing that culture. A School Board (elected by a tiny minority of society who are in-the-know), are typically made up of the local royalty; wealthy people who control industry and decide what type of workforce they need to crank out of our #PublicSchool's. The Superintendents serve at the pleasure of the school board, and the Super has all the hiring decisions on the Principals, so the type of person is easy to control. Principals secondarily serve at the pleasure of the school board and make all the hiring/firing decisions for the people entrusted to take care of delivering education to our children. If you or your children notice an authoritarian bent to your designated public school, it's there by design, not by accident.
The gap between an ordinary #American's experience in public schools and the time they can really judge what the hell happened while they were there is about 10 to 20 years. While you are in the institution, you don't have the life experience to judge your own experience. The few memories you have of that 13 years of your life are focused on the interactive drama with your peers, not on the tragically unhealthy system designed to make you into dutiful clock workers who do what they're told by middle managers after you graduate.
I have personally been in the armed services and was a certified math teacher for NYS schools K-12. I got my certificate from a University instead of a College. The main difference is I was steeped in the ideals of education and the possibilities for the learner gaining and benefiting from the advanced knowledge, whereas the typical college trained teacher is gifted with the Machiavellian rules of power in the school. As I worked in our public schools I couldn't help noticing that they had an uncanny resemblance to military boot camp and the command structure. I would rate military organizations slightly better based on personal experience. I've run into unethical practices in both that made me shudder, but never expected it in schools; rampant incompetence, rule one is cover your ass, rule two is screw-your-coworkers, lots of #MeToo shit going on, psychological abuse of the students, enforcement of removing freedoms from students that they have on paper.
Their's even a bit of prison culture running around schools. That favoritism of the big violent types that the guards can control happens where the favorite jock (soon to be a rapist) gets favoritism by faculty and staff in order to be pointed to giving beat-downs on subversive types in the school (artists and creative thinkers). High-school click's and prison gangs are about the same thing, just with less physical violence in school.
We would think that it would be common to hear about this in the news sometime, right? Well, the few places I worked had gag orders as a condition of employment; you aren't allowed to say anything bad about the school system to anybody at any time or you will be terminated. Sure, you could talk about it after you are fired... ...if you want to flush that college degree down the toilet and never work as a teacher again.
If you learned about the history of how American schools changed from little prairie houses to the massive factories we have now, you would see that it's all about wealthy industries controlling costs. The first pitch to create schools was that they could turn those shiftless farmers into clock-workers who could calculate correctly, as well as read, write & follow orders. American Public Schools had the same moral foundation as a horse ranch that captures wild horses and breaks them so as to hitch them to carts, covered wagons, and cannons.
I have had many fond memories of teachers who were doing the right thing within a terrible system but they are a small portion of my total educational history in America. I have many uplifting experiences with teachers who my children learned from too, but those are not part of the system by design; those are good people that get through tenure before they start doing the morally right thing for their students.
We are coming up on the end of the #BetsyDeVos era.
Her tenure is like a super-hurricane, earthquake, volcano directed at the public schools to make them worse than they are, weakening the negotiating position of most future working Americans, strengthening the position of private industries control over the curriculum, as well as religious influence so as to have a better bit & bridle on the students thoughts. I can only hope that true progressives will attain power in the coming election and have an epic rebuilding effort after the damages done during the #Trump administrations reign of terror.