I went to a grammar school, which quadrupled in size when it went comprehensive ( I was 14 at that time.) Learning had been valued and behaviour, certainly in class was good. In the comprehensive, learning was sneered at, the teachers could not control the classes. The school is now a 'sink school' and parents who want a learning environment are forced, if they can afford it, to pay for private education.
I went to university, but children from that school do not now go to university, so has severely hampered the prospects of those scholdren who want to learn but whose parents cannot afford private education.
When I was at the grammar, hardly any private schools existed in that city, there are now many.
For my own children, all I want is for them to in an environment where learning is seen to be a good thing. If they get into the (one!) local grammar, then fine, otherwise we will pay for them to go to a school where they will mix with children whose parents instill a respect for the school and learning - most will not be rich snobs, ( can just anticipate flames on this) but people who are prepared to prioritise their spending to education.
Sadly, cannot help those who simply don't have them money - shame that successive governments continue to let those people (who bear proportionately the hifhest taxes) down.