it will stop producing terrible self serving politicians that don't fund state education properly good grief. The majority of independent school DC don't even go into politics, let alone all have the same opinions. Writing independent school DC off as a mass of braying billionaire Boris lookalike toffs is a shitty attitude toward children. The DC do all sorts and aspire to be anything including teachers and doctors, just like teenagers anywhere. And the fees go back into the economy via teachers salaries, supplies etc too, they don't vanish into a billionaires back pocket. And foreign pupils bring money into the economy too, there's loads of them.
My DC at indy has friends from all walks of life, their best friend's parent is a state school teacher, another friend is Finnish, they have a Mongolian friend, its much more multicultural than our local comp. The difference is their friends don't all live in a fixed radius of their school.
A very vocal and very left-leaning teacher I know lives in a house worth 4 x mine to send their DC to the leafiest comprehensive for 50 miles, they talk the big talk but have discreetly gamed the system. And they complain to and about the school all the damned time and get nowhere. But somehow me, in my crap house but using my own money to put DC in fantastic schools they're thriving in is doing something monstrous by comparison. Its ludicrous, I could home ed but not be able to work nearly as much which means I'd pay less tax, so why is that more acceptable? Anti-indy is a straw man argument.
The British state system is just one way of educating but its far from being the only way, to think it should be is overly simplistic and not in the real world. Put 500,000 DC from indy schools into the state system and it would be a disaster in an already overwhelmed system and the already overwhelmed teachers would bear the brunt.