This "elephant" is a racist opinion of your own making. Parents want to send their kids to a school where their peers will influence them to be good students. And as anyone who has gone to a largely "non-ethnic" school can attest, the racial makeup of the student body is far from a guarantee.
How is it racist to point out that out - what next being called racist for pointing out that BME people that get stopped and searched more than whites?
The guardians own articles on property make a point of highlighting "good" schools when they cover an area?
Parents good intentions can often go out of the window when it comes to their children - I recall my mum commenting that if we had stayed in Birmingham she woudl have tried to get me into King Edward VII via family connections.
King Edward VII being the top selective school in the UK
And yet everybody who can afford it, sends their kids to private schools in London. Heck - I know people who sold their house so that they could pay for private schools.
The intent usually seems to be to get one's chidren surrounded by primarily middle-or-better class children, not to keep their schooling racially and culturally pure.
I don't think the original post indicated a desire to keep one's children "racially and culturally pure" but rather to avoid sending one's children to schools with large number of non-Whites, for any number of reasons.
It's not a race thing but rather class. People want their children to go to school with отчер kids who are smart / motivated to succeed - hence will focus on school.
Best determinant of that are the parents themselves. So private schools end up being essentially a sieve that checks parents. In the US parents move to the suburbs with high local taxes that fund good schools for the same purpose.