The teacher's unions protect teachers at the expense of students. Basically the union doesn't care - at all - about teaching students (it's for the teachers, after all). They only care about stopping teachers from getting fired. It's our youth that suffer from receiving a shitty education. The assumption that "the teacher is always right" is profoundly damaging to our youth. The decline of the American education system (below college) is well studied.
https://hechingerreport.org/third-indication-u-s-educational...
Just to throw out a counterpoint, there are some who feel the education system is not declining, although I disagree. I encourage you to come to your own conclusions.
https://www.washingtonpost.com/education/2018/10/15/how-are-...
There's a movie about it if you want to watch it:
https://www.imdb.com/title/tt1566648/
Yes, it's a documentary with an angle, but there's enough information in there to convince me.