I havent been able to read through everything properly - what a lot has been said- and some on the French education about which I know nothing.
However here are some thoughts:
The metro newspaper mentioned that pupils from independent schools are 55 times more likely to receive an offer from Oxford compared to those who receive free school meals at a state school.
Therefore I think that outreach mentoring should be targetted at the poorer pupils. I suspect they are disadvantaged by having no desk, no books, no internet, no family support, no food, no stationary and no peer support amongst other issues. The public libraries these days are very variable and some have wretched literature sections.
Access to the internet has resulted in more equality of opportunity in terms of educational materials/ exam board specs/revision tips/past papers etc. Therefore it is possible for a well organised person at any school to achieve 10 A stars at GCSE. However that person has to have the organisation skills of Mrs Moneypenny, unlimited internet time and/or a good memory for what is said in class, and a bit of stamina to take the 30 or so papers and achieve consistency. Also the revision time respected by the family
A level teaching is very variable and here is where the type of teacher and probably, but not inevitably, school begins to make a real difference. Families can seriously underestimate the challenges of the A level years especially the Autumn UCAS term, especially if no one has been to university. Students need support in terms of money for the extra books (never in the library) and society talks/lectures that they need to go on. Families can easily underestimate this. Nevertheless I think there are many students who have a very real passion for their subject and an insatiable curiosity.
I think the Oxford interview process - particularly the second college interview policy/ pooling criteria is coming across as rather variable in some subjects, and could possibly do with an overhaul. It also seems to me that interviews are possibly not allowing for the quieter pupil or the pupil who has an interest which does not co-incide with the interviewer. This might be a state or a private school pupil or an ethnic minority pupil.
For example Ponders mentioned that her DS had a 'flat' and unchallenging interview. My son had a similar experience. I have heard of lots going for the humanities who had a similar experience. This is understandable as it must be tiring to interview so many and hard to interview the quiet ones and in any case tutors are looking for those who are easy to teach. Nevertheless I think it important to give all a variety and breadth of questions, especially in the humanities, to enable the able to shine.
A chance of 1 in 10 is not serious competition. To get a good post grad job as a medic in this country is over 100 to 1, worse odds for banking, even ordinary posts in Waitrose are worse odds. Bristol psychology odds are 80 to 1.
So really anyone who can't be bothered to prepare properly for at least a few months for a one in ten place doesn't deserve to get in.
The problem is to distinguish between those who cannot be bothered and those who do not have the resources.