When children are constantly receiving the message “school is a waste of time, don’t bother trying” it’s exceptionally difficult for teachers to overcome that in class.
Politically no one wants to grasp it because conservatives like to talk about parental choice, as if every parent is well-informed and usefully involved, while the left doesn’t want to accept that some people won’t help themselves.
This then perpetuates from generation to generation, people see the success of immigrant children whose parents value education, resentment grows etc etc.