If you want your kids to go to good schools there are roughly two options: you can choose your town for its schools or send your kids to private school. I went to a public elementary school [1] in Medford, a town not known for the quality of its schools, and around third grade my friends started leaving. Their families were moving for the schools, out to Lexington, Bedford, and Newton. By the end of fifth grade I was the last of my original group of friends still there.

For middle school and high school I went to private schools, which were much better than the schools in our town but similar to the ones in the richer suburbs my friends had moved to. Compared to moving, this meant paying more in tuition but less in housing. The calculation to figure out where you do better economically is a little tricky, but not too bad, though getting a sense of how good the schools involved are is hard and determining the importance of a good school is even harder.

Occasionally people will say it's wrong to send your kid to a private school. For example:

if every single parent sent every single child to public school, public schools would improve. This would not happen immediately. It could take generations. Your children and grandchildren might get mediocre educations in the meantime, but it will be worth it, for the eventual common good. -- source

The idea is that if rich parents were sending their kids to public schools they wouldn't stand for poor quality education. They would get involved, demand change, and make things better. The problem is, if you tell people that private schools are wrong they won't substitute random public schools. Instead this same drive to have the best for your kids coupled with the means to afford it would mean expensive areas with good public schools.

You could demand that people send their kids to public school and live in poor areas. Then this dynamic where rich people wanting the best for their kids would spill over into helping other people's kids. But that's a big sacrifice and few people would make it. [2] So instead you say "if you send your kid to private school, you're a bad person". Unfortunately this doesn't change behavior in a way that makes schools better for poor children. Instead the people who are already sending their kids to public schools, perhaps because they can't afford something else, perhaps because they chose an exclusive expensive town with good schools, feel virtuous and just for doing what they were already doing.

[1] One of 12 neighborhood elementary schools, now gone. There was federal money for building new schools but not repairing old ones, so the town built two large elementary schools and sold off the small ones. It's now condominiums.

[2] I also don't think people should make it. Moving to a place you don't like to send your kid to a school you don't like is painful, and for rich people there are less painful ways to do much more good, like donating to effective charities.