Off the subject a bit, but this is interesting
"Women working in that field are bullied out."
Observation is that British girls seem to stay away from quantitative subjects, but that this is not true of Asian girls, particularly Chinese, or Europeans (again noticeably Hungarians/Russians and Poles). Is this observation accurate, do the non British girls simply stall at a later point, or is there something happening in our school system that is causing white or black girls to lack confidence.
I also agree that judgements are not clean cut, and that lack of representation of some groups is often something that cannot be fixed by University admissions. Instead of blaming Oxbridge, Lammy might have taken a more constructive approach of identifying a "problem" and considered causes and solutions.
And DS will be fine. One of the really useful things he gained from his education, more from his international peers than from the school itself, were high aspirations and a belief that these can be achieved with determination and hard work (and some talent.) Also the school's basic advice was to aim (realistically) high, but treat it as a two year process. And we know at least a couple of kids (same subject) who did not get one of their top choices first time round, but got Cambridge on reapplication.
And perhaps part of the answer. London kids are growing up in a world city, quite a tough place to earn a living, and so are both ambitious and realistic.