[quote=MalayHKGBut the thing is the majority of people who gain places to Oxbridge come from independent schools and they significantly outnumber the number of state school students. 7% of the British population are privately educated, yet 50% of Oxbridge students are from private schools.
You say attendance to Oxbridge is an indication of academic attainment, but the problem is that the people who attain these grades are all privately educated which is absolutely preposterous which signifies that wealth plays a key role.
The larger part of this is correlation and not causation.
Students who go to public schools and then on to Oxbridge almost invariably come from families somewhere between affluence and staggering wealth, in which discipline and self-confidence are instilled at a young age and they are raised in atmospheres of learning and culture and given tuition either by their families and/or by private tutors.
I think that last one is especially underrated. I did not receive any home tuition at all during my school years, except on one occasion when I visited a privileged friend in Germany during a holiday. This was prep/primary school. I was in the bottom set for Latin, scoring around 45% in tests and generally pretty crap. His father was home at the weekend and he tutored both of us through Latin for a solid two hours or so for our Common Entrance mocks...I ended up getting the highest mark in the year when we went back.
Playing fields, old buildings and slightly smaller class sizes have very little relevance to the numbers of private school students at Oxbridge except insofar as they are a reliable indicator of the material advantages behind the scenes.