Why are most primarily black schools functioning so low?

Most primarily black schools (grade schools not college) are way below the standards for the average student in the US and we see that blacks who attend white schools have significantly higher scores than blacks who attend black schools thus we know that black people have the capacity to be just as intelligent as anyone else. Why can't the inner city schools emulate the programs in the white schools? If they are already doing that then what is the problem? under funding, bad teachers, not enough courses and extra curricular programs? No motivation, hopelessness?