The biggest problem is the parents. They don’t raise their kids — they think the day care will do it, the elementary school will do it, the high school will do it, the television will do it. Some parents expect public school teachers to toilet train the child. It’s downhill from there.
The “experts” who design curriculums (heavy on political indoctrination) are a big part of the problem.
The Administrators who don’t really care about either students or teachers are a problem.
The Teachers Unions are a problem.
And the teachers are a problem. I don’t know how other states handle it, but in MA, if you want to be a teacher, you need a Masters in Education. In order to teach math or history, for example, you need to spend years in higher education learning about creating lesson plans, classroom management, and critical race theory. But you don’t have to learn either math or history. Just teach the stuff you don’t know.
Public education is as broken as can be. At every level. Top to bottom.
Or, more likely than not, the biggest problem is the parent, singular.