At Newstead school for girls, a state grammar in east london, my friend was telling that their upper sixth, of which she was a successful part, got 25 people into Oxbridge, with a notable number doing Classics. Apparently they are the best state school at getting people in in London...
At my school, Christ's Hospital (the coolest school in the world), we had 32 applicants and 11 were accepted... I reckon our figure of an 1/3 success rate must be pretty standard.