It bothers me enormously, Bonsoir, because anything like that contributes to a collective perception that application to Oxbridge is not worth it unless your background is 'right'. So, lots of kids from less privileged backgrounds who DO have the academic aptitude to get in, simply don't apply - because they, their teachers, and/or their parents don't believe that the dice aren't weighted against them.
And it is a vicious circle - the fewer applicants we get from less privileged backgrounds, the more disproportionate our intake is, and so the illusion is perpetuated.
So year after year, we don't get the opportunity to interview bright kids because they haven't applied.
That's why it matters - much more than because there is an individual case of disparity.
Cortina - I can well believe it happened in the past - but I do want to emphasise that scrutiny is much better these days, and it just doesn't happen any more. Of course, if schoolteachers are prepared to seek to deceive the universities, there are so many other ways they could do it...you can't JUST go on the interview alone because that would be unfair to (e.g.) someone who found it terribly intimidating, but nearly every other means of testing ability could be interfered with by the school.
Benign - that's interesting - haven't come across them, but then, circumstances under which you think an obviously able student wouldn't achieve the grades must be pretty rare.