Just because a course has quite a low applications to places ratio doesn't necessarily mean that the applicants are less well qualified, and the university examinations haven't been made any easier because of it.... I'm sure if you looked at Oxbridge classicists' GCSEs/A-levels they would be about as high as any other Oxbridge students'.
The number of applicants for classics has been significantly increasing over the past couple of years, owing to more state schools offering at least Latin, unis starting to accept students with no linguistic knowledge, and the subject seems to be losing its old-fashioned image.