When I was a kid, my mother was very clear. "When you are in school your teacher is like your mother." Your teacher would not punish you unless you did something wrong. And if you do something wrong at school, you will feel consequences again when you get home. Translation, your teacher is always right.
Fast forward, a long time later. The new message to kids is, "that teacher better not hurt you, holler at you, catch you doing wrong or I will be in that principal's office in a heartbeat." Translation, your teacher is always wrong.
Neither approach is correct, but if I had to go with one, I would pick my mother's advise. I say that not because I think of myself as a teacher or because my mother almost always gave perfect advise, although both are true. I lean toward teachers being on the side of the angels more times than not for lots of reasons.
Firstly, teaching is hard work and not for the faint of heart. Mostly people become teachers because of the kids and because they want to help children be better. Even with the vastly improved salaries a person will never become breakout rich teaching school. So there have to be other rewards.
Secondly, I freely acknowledge there are lots of lousy teachers who bully kids and like the feeling of authority over kids. Every barrel has a bottom and some teachers live there. However, whatever negative things are true about teachers' personalities are also true about the personalities of bosses kids are going to encounter when they grow up. So they should learn to manage less than fair treatment. And NO, I am not endorsing bad teaching as a good learning experience.
Thirdly, parents and teachers need to be on the same side of the battle to produce fully functioning good adults. With all the distractions today, that is not an easy task and both parents and teachers need each other to fight along side of them.
Lastly, the teachers are always wrong position is bad for kids. Human beings, including kids, need to learn to take personal responsibility when they mess up. This acceptance of responsibility is key to a good personal relationship, good work experience, and a positive outlook on life in general. It does kids no good to think that there will be a parent or other powerful figure ready to rush in and get them off the hook when they do something wrong. Our jails are filled with people who think the rules do not apply to them and if they do, well they will still get off.
So in standing up for teachers, parents are also standing up for a good future for their kids- and who doesn't want that.