I have been musing on this today, particularly the suggestion that if you can pay, you should, and otherwise you are using your child as a guinea pig, and not allowing them access to facilities, opportunities, etc. The situation for my daughter is quite interesting:
There are 4 families, all with girls the same age, in our village who we're good friends with. We're all planning on sending the girls to the local state primary and secondary schools. Assuming things don't change drastically, these 4 girls will have access to the expertise and assistance of: a chemistry professor, history lecturer, 2 teachers, biology and English PhDs and a GP. My daughter will have access to lending rights at at least 2 good universities, sports facilities which will have been used by teams training for the 2012 Olympics and 2014 Commonwealth Games. She has enthusiastic and committed parents who are both education professionals.
I really don't think that by sending her to state school we're denying her much at all, apart from access to an old girls network, which I do find morally suspect. I think her education in manners are our responsibility, and one we take very seriously. She will speak with her local accent, and will learn, with our help, to express herself in a clear and articulate manner.
This is just one example, but it's true at present for these 4 little girls, all of whose parents could pay for private education, but are choosing not to. Yes, we all think the local schools are fine, and so it is easier for us, but I do think that it illustrates that the issues are not as black and white as has been suggested elsewhere in this thread.
Now, this is also at a tangent to the question of whether private schools should be banned, but I thought it pertinent, as there's clearly a lot more to education than school.