Every day during school term time I drive past one of the most prestigious private schools in the U.K. It's right next door to my dc's comp. The private school is beautiful, with enormous grounds, state of the art science labs, several playing fields.
My dc's comp has double the number of students crammed into a site half the size and no playing fields.
You can see the difference between the kids. The ones at the private school are taller and slimmer, and mostly better looking.
It deeply offends my sense of justice to see such blatant, ugly inequality between children laid out in front of me every day. To know that the children at the private school already have much, much more, even before you take their expensive education into account, and yet being clever, tall, healthy, well supported - it's still not enough. They have to heap privilege upon privilege.
The existence of private schools is morally indefensible at a population level. I understand why people want to send their children to them, but society shouldn't do one single thing to support or perpetuate such a morally appalling system.