Joan I suspect you don't give a flying fart, but here goes anyway.
My kids are no doubt privileged (before we get to the school). Both parents in a stable relationship, highly educated, speak a couple of languages, play instruments,in gainful interesting employment, earn plenty of cash, house with land and full of books/music yadda yadda.
Already far far luckier than the vast majority of kids in the country.
So why would I need to send them to a private school? The answer is of course I don't need to.
Just like I don't need a lot of things.
But life is not about need is it? It's about joy and stimulation and expansion. It's about making the most of yourself and the world around you.
And personally, I feel that by sending my DCs to the schools that I do, I am doing those things.
It is not about results. Or avoiding poor people ( I suspect I started out my life much poorer than the vast majority of hand wrngers here on MN). It's them enjoying the ride.