The teachers’ unions hate charter schools because they are non-unionised. And politicians depend on the money and votes of teacher unions. Politicians(leftist) also dislike charter schools because of how it threatens their ideological vision on how schools should be ran.
Example, Attorney General Eric Holder wants to force his own idea of racial balance in the schools, while many black parents just want their children to learn, regardless of whether they are seated next to a white child. There have been all-black schools whose students met or exceeded national norms in education, whether in Louisiana, California or other places around the country. But Eric Holder, like Bill de Blasio, put their ideology above the education of black students.