An affirmative action policy only can admit students - it can't prepare them and can't guarantee their success. It is no surprise that, academically, students from lower socioeconomic backgrounds fare worse than do those from wealthier upbringings. Higher income means more property taxes, better schools and so on. Moreover, these wealthier students may have access to better outside resources, such as SAT prep courses or private tutors. This problem also is connected directly to urban flight.
Families move towards suburbs as they earn more money - often in search of better schools.
Meanwhile, their departure makes it impossible for the neighborhood they leave behind to grow economically. But the issue is not just one of social class. Far too many families in the lower economic category are minorities. But to think the problem can be solved with admissions policies is naive. An affirmative action policy only can admit students - it can't prepare them and can't guarantee their success.