I think it's because we as people tend to speak from our experiences, and I do agree that school is more authoritarian than it should be.
I'm not sure what else you can do :( it's a really big systemic issue. I think we just need more awareness, first?
Social life in prison involves having "friends" who can any day decide to try and rob or fight you (both happened to me with my closest "friend"). Nobody has real friends. It's dog eat dog, you lose the ability to trust, and don't have any trusting social connections. That's extremely painful. When you talk to people on the outside, every prisoner just tries to deceive them into thinking things are just dandy: I'm not sure why that happens, but it means those connections aren't real either. It's all so much worse psychologically than is conveyed in popular media. We don't know how to quantify psychological suffering though; as a society we rather put people through huge amounts of that than some visible physical suffering (which, again, is probably strongly preferable to the criminal).
Unfortunately most of the people suffering in the prison system are poor, so we don't hear what they have to say. If you're rich, you can afford your own lawyer and get a much better plea deal, and get out quickly. It's also very racist: you will really understand Black Lives Matter when you meet a black father who was sentenced to 30 years in prison for a nonviolent drug offense, and realize there are 100,000s - millions of people in the exact same situation: it's destroying entire communities. I've seen the way black people who a judge has never seen before are villified from their appearance: go to a courtroom near you if you don't believe me, it's shocking. I'm talking about in San Francisco, not even a rural area.
Anyways, thank you for your empathy. I wish more people understood that criminals will commit less crime if they're forgiven and accepted by society, instead of villified. And it's also the decent thing to do. Prisons are bad cultures because the small number of actual bad actors push everything to this shitty equilibrium: most prisoners individually have a lot of shame about their crimes, and as strong a moral code as the average person. Some definitely do not: and it's hard for the justice system to make the distinction.
All things which are hard to believe until you have some real world experience with these things...