It's shit like this that makes me feel so lucky to be able to get a scholarship to an excellent private high school. It's a privilege I certainly recognize and I wish others could have the same educational opportunities I did. Schools don't have to be like you said. Some heavily conservative private schools are probably worse than public schools, but for me, high school was better than undergrad and graduate school.
The Pledge was never an issue for me because I've never been required to say it, and frankly I don't even know the words. The teacher I had for Physics is a heavily politically active mutualist/democratic socialist. He was in university during the Vietnam War, and apparently he was so exceptionally anti-authoritarian that one of his professors called the draft board and told them that they did not want to draft someone like him. My US History and Constitutional Law (which ended up being entirely civil rights law) teacher was a former ACLU lawyer. My conservative father was not happy that she'd assigned us Howard Zinn's A People's History of the United States and gave us "Question Authority" on a red and black background bumper stickers as a prize for having completed her (highly demanding, 3 hours of homework a night) Constitutional Law class. The year after I graduated, there was a new head of school who thought he only had to answer to the board. The teachers rebelled and he was fired quite quickly. That school has such a great culture.
On a tangent, that experience also taught me quite a bit about privilege. One of my friends there, a dorm student from China, in the context of that school and without nearly as many of the privileges he enjoyed at home, was one of the kindest people I've ever known. After I graduated, I visited him in Beijing and he was a huge asshole. I learned that his uncle was Beijing's chief of police and that being abusive was his way of getting an adrenaline rush at home. He'd been arrested numerous times for it, but he had his uncle on speed dial to get him released. He was like a completely different person and I've never been able to look at him the same.
It's also quite revealing how different a bourgeois school is from public school.
Solidarity to those of you who had/have to put up with shitty schools.
TL;DR: School can be an incredible experience if it is a good school. It is abhorrent that most schools are aweful.