Charter schools in Miami are allowed to expel students permanently. They are allowed to exclude students with special needs, both physical and mental.
Parents who have few years of inferior education often do not insist that their kids study. They are not the only ones, of course. A large percentage of Black people in Chicago have migrated there from the poorest and least educated parts of the country: notably, rural Mississippi. Education for Balck people was pretty awful throughout the South, but Mississippi and Louisiana, especially the rural parts, have the worst schools for Blacks and Whites alike.