I think what is interesting about this thread is that many of us who have had a good state school experience (either for ourselves or our DC) are not going to be anti private school. We understand that the private system is separate and often could benefit from it if we lived locally and used their pool, netball courts, tennis courts, cricket nets, extension clubs for local kids etc.
I would have been happy for my DC to go to a secondary school with all the kids from our church primary (rather than the grammar). What mattered is that they came from families who read with their children regularly, did the homework, supported the PTA and were polite to the teachers. I would say at KS2 often almost 45% of the class got to greater depth. In the grammar we had a lot of Asian parents (Indian, Chinese, Japanese, Korean mainly) - again, it didn’t matter that not all were well off, many actually lived in flats and worked all hours and were not all professional middle class types, at all. What mattered is that they strongly encouraged education.
Meanwhile, I also live in an area where there is a primary school where parents do regularly show up with the types of dogs I don’t like, shout, swear, smoke and yes, some do show up in pyjamas. It is an utter cliche, of course. Some of the kids from those households can be fine in primary but more often than not, they switch off education in secondary. Unless they really have amazing teachers. But children are only in school for 6 hours a day and 18 hours at home, including the holidays.
What is also really unfair is that some children who are nice, from nice polite families who are not rich can only end up in school with a large amount of children with the former profile. Of course, I feel very bad for them and I expect government to do something about it. However, I don’t think it is my job to send my DCs into that type of primary or secondary and I don’t think it is the fault of private schools either. This is why additional funding is required for those kinds of schools and I think it is better to get help from the successful schools (be it state or private) rather than attack the better schools.
What I would like to see in schools with demographic challenges is smaller class sizes, streaming, lots of one to one attention, better paid teachers to encourage some who want to make a big impact on a deprived child’s life. Which can be done if there is enough time to give them actual attention.
There is also the option that has been tried in some comps which is zero tolerance of bad behaviour and really strict uniform policies and blazers. The problem with that is that often only quite motivated parents end up sending their DC there so it is often a back door selection too.