It isn't that simple. The public high school I went to is one of the best in the country and was largely comprised of middle class and upper middle class families. The very wealthy largely sent their kids to nearby private schools. The parents of the children at my school were largely professionals / tradesmen / small business owners, worked incredibly hard to get access to the school district (I know mine certainly did), and placed a large priority on education. This resulted in a culture of parental involvement in the schools / their childrens' education and a competitive academic spirit which kept standards high. High property taxes also produced a funding model where at least 95+% of funding was coming from local taxes, local bonds, and communal fund raising by engaged parents. Local people supporting their community schools because they cared. These were being levied against regular homes as well as large homes.

There were attempts made to bus in people from outside but they were fought tooth and nail by families across the income spectrum in the district because the perception was that it was unfair that they had to work extremely hard to get access to these resources but other people could simply show up and get it for free.

I'd be very curious about any study about outcomes for good school-type kids (i.e., ones whose parents could afford to buy a nice house and send them to a good school) who go to schools in poor neighborhoods. Does anyone know of such a study?