We have such a range of schools in our area. I think it does depend on the area, school and intake. In our area, we have some of the top grammars in the country, with some absurd number of children vying for a place, a very good Catholic girls' school and a less good Catholic boys' school, an excellent sixth form college, an "up-and-coming" academy run on pseudo-military lines, a bog-standard comprehensive and a (by all accounts) awful comprehensive which now has a new head and is having additional resources poured into it.
There is also one of the top private schools in the county, an "alternative" private school for children with whom mainstream education doesn't agree, an SEN private school and very good girls' school. However, the girls' school has the reputation of being somewhat pressured and the top school has an incident recently which many feel has called into question the quality of its pastoral care and the stress that the children there are under.
It is possible for a child living in our street to end up in any of these schools depending on ability, need, parental preference, income, gender and religious affiliation, amongst other things. I realise that it may be unusual outside of densely populated urban areas to have such a range of schools.
It's very difficult to say that any children in our area are "missing out" purely from not going private due to the range of private and state schools. Certainly the grammar schools have great facilities (swimming pools, sports courts etc) and parents there would probably think they were getting a "private" standard of education for free. Meanwhile the two comprehensives have quite limited facilities in comparison and both have been implicated in the crumbling concrete scandal. The SEN school obviously caters for children with particular needs and the "alternative" private has quite a limited range of resources compared to the other schools. And there are quite of lot of parents who are relieved that their children aren't in the pressurised atmosphere of the local privates and they don't have that financial pressure.
It's very difficult to work out who is missing out on what! I'm glad that we still have a few years until we have to consider secondary options for DC1 because I must admit I'm flummoxed by it all.