This puts the debate over school vouchers in a whole new light for most of us here:
You mean because if there were school vouchers, these schools would be less white? They aren't "segregation academies" if they have non-white students, as the article admits they do.
Most “Christian” schools in the south were founded by wealthy whites to keep their kids away from black.
Wealthy whites don't have to send their kids to black schools because they can just move to places that don't have many black people. Most Christian school families aren't particularly wealthy, certainly not compared to those who go to secular private schools.
An important confounder in all this discussion is that the era of school desegregation coincided to a large degree with the era of school secularization with ending things like teacher-led prayer in school, both results of the Warren Court. So you can't look at a private Christian school that starts in the South in the 60s and 70s and assume that reaction to civil rights must have been the motivation.