I see what you mean MD, but that brings another point to the table - the issue that most private schools are christian and you often have stringent requirements to get in that makes it difficult for immigrants. This means that a lot of private schools naturally filter out immigrants, even if they might want to attend. I am Catholic and had that issue when looking to place my children in a private Catholic school - I'm Catholic but my children were not baptised and therefore they did not get placed high up the waiting list. They eventually did not attend a private school in the end - they could not get in.

It also means that, as a result, private schools tend to be more culturally homogenous than other schools. I lived in an area in Perth that had a high density of immigrants (asians) and while the public schools were 50% or more asian students (and ranked in the top performing public schools in WA), the private school that was in the area had a very low percentage of asian students. I don't think immigrant parents are less inclined to care about the education of their children, but private schools are often not geared towards permitting easy entry of immigrant students into their ranks, with waiting lists and other such barriers to entry.

And I don't necessarily agree that the choosing of a private school when in a high density immigrant population is explicitly racial quarantining, and I said so earlier. But I think it's a by-product of it.