The counterbalance to a union and to management needs to be customers, but customers aren't able to vote no here. That's fundamentally undemocratic.
And you end up with terrible outcomes like collapsing literacy rates through the prevention of teaching phonics, which leads to parents opting out of public education entirely. There needs to be a feedback mechanism in unions for them to work.
What is your evidence that teachers’ unions are causing these issues and not state/federal education policy? Do teachers’ unions have a big role in developing curriculums or setting educational policy? It seems like state legislatures and superintendents have more to do with that.
If you want evidence, look to the Teachers' Unions own efforts to oppose phonics education: https://www.edweek.org/teaching-learning/why-some-teachers-u...