I went to St Clare's on the Banbury Road to do the IB. It was brilliant: I had a lot of trouble at my secondary school, and left at 16, but St Clare's was a very sympathetic and caring environment as well as an intellectually stimulating one. Unless you happen to be extraordinarily rich, you'd need to try out for a scholarship: most of the local kids who go there tend to be on scholarship: board fees for non-scholarship students are I believe higher than Eton! But it's a great place to do sixth form stuff and a good springboard for getting in to the top universities, especially because the IB appears to give you a more solid academic background than A-levels.