The real estate company Trulia has a series of charts on private school students, who make up about 10 percent of all students enrolled in school nationally. Here's a map on where private school is more common:
The most telling chart, though, is this one. It looks for demographic characteristics that usually make students more likely to attend private school — well-off, highly educated parents — in neighborhoods with high-quality public schools and low private school enrollment rates. Basically, this chart shows how much it costs to live in a neighborhood where parents choose to send their students to public school even though they could afford other options.
The sample sizes are small, but the message is clear: a really great public school isn't cheap, either.