Ronaldo - surely your point about private schools is partly due to smaller class sizes, entrance levels of pupils, disposable income, engaged/pushy parents, work ethic and level of competition? The fact that many teach purely to pass exams may also play a part but this may be controversial.
Actually I think it is a myth (one promulgated on MN too often although I have avoided the controversy) that all the parents of DC in private schools are asyou describe above or that the schools have highly selective levels of intake and "pushy" parents.
Frequently the differences between DC in state schools and those in private ones are similar to each other and as diverse. Not all have pushy parents. In fact many in our boarding dept are dumpred by their parents who want lives free of their DC. Many more are dumped on us because their parents are ashamed of their lacj of ability or they are challenging in some way behavioiurally and we have to sort it out. many more day pupils are dumped on us and we are expected to superbise homework ( prep) and offer support because the parents, frankly are CBA.
Thats the hard reality. I agree we have smaller classes. I agree we have parents who come from slightly higher income groups beyond that, little is different than in state school.
We do instill as schools an ethic of work and of pride and often DC thrive with us because of discipline and no DC with challenging behaviour. DC with challenging behaviour are invited to leave us very quickly. I know most independent schools will operate similar systems in many ways - especially those who do not select heavily ( many despite what the myth says).
But we are nearly all free of the NC. This does allow a balanced curriculum , not one which is crowded with political correctness and too many subjects and a policy of teaching which never seems to do more than place rootless flowers in pretty vases. Often less is far more in the long run.
Not many parents really know what independent schools do and dont teach IMHO.