Earlier quoted context omitted.
Aren't schools financed by local property taxes in US. And the rich parents pay more in taxes and there is more resources in the system. Also well off parents could help school in other ways.
Accounting for local, state, and federal spending, most states spend more money per student in their poorest districts than in their most affluent ones: https://www.washingtonpost.com/news/local/wp/2015/03/12/in-2... . In California, the poorest school districts receive almost 14% more money than the richest ones.
Plus, in the case of NYC, rich PTAs more than make up the difference between what the state provides and what the students receive.