This is a very deep seated problem. For example, all public schools must be accredited as are teachers. Guess who controls the accreditation committees, guess who gets the legislature to grant them a monopoly function. The public teaching establishment via their fellow travelers in the various teacher's colleges and teacher's unions. This collusion is also supported at the Federal level where funding is impossible to secure unless the right people approve, people who support the leftist status quo.
It has taken generations for the left to become to well entrenched. Meanwhile, children must be educated but protected from the propaganda. The only answer for now is to escape the system, even as people work to change it.
My wife ( a conservative) went to college for teaching. She took the courses, passed the test and became a teacher. She was never asked about politics...you guys see a conspiracy where none exist.