Ah yes, it's the best choice for your child to only socially interact with the same social class and, by total coincidence, exclusively white people. It has nothing to do with "what's best for your child", it's purely based on separating social classes and keeping up the divide between groups. Nothing more. River will grow up in that system for the sole purpose of finding equally rich friends and a rich partner to marry later on. This is not about her education or actual well-being. Nor is it for any other kid that's being sent to private school or boarding schools. At least one of the women I worked for in London was honest about it; she and her husband spent all their money on their kids' private school fees so they could form friendships in higher social circles. I remember her telling me (in front of one of the kids) that there were "many important children" in the daughter's class. Meaning, they were the kids of celebrities, politicians and other wealthy people.
Having said all that, it's the least surprising thing about Fleur and Mike that they would send their daughter to an expensive private school. What else would they do? :-D But I think it's totally ok to voice one's opinion on that