Retro the Spectator blog makes some good points but I'm not sure it has all the answers.
The whole rat race/ competition case sounds a long way from the influences in many families in my borough where a huge ratio of families have never had an employed adult male. And in terms of museum and cultural uptake many of the disadvantaged kids have never ever been taken by their parents - the museums and central London feel a million miles away, culturally. Though obviously easily accessible to those who use them, especially since London offers free bus travel to school children.
I also agree that diversity actually adds something to education but there as many disaffected black boys engaged in or victims of gang activity as there are children of aspirant and hard studying Jamaicans or Asian Tiger Moms.
The house prices in London don't automatically mean that it is the rich and wealthy who live here. Huge numbers in social housing, huge numbers of people in ordinary jobs squeezed into small flats and under pressure to pay the mortgage. Huge numbers of families which do not have the luxury of a sahm who can take care of tutoring within the family because of the need for both parents to work f/t to pay the rent or mortgage. I think it all mitigates against the perfect environment for educational success as well as supporting it.
I do think though, that while many mc parents are concerned that their children will be distracted or disrupted by children of lower socio economic groups, what actually happens is that children who will do well will do well - but the fact that everyone is different in London school means that no one is restricted as to who they use as a role model. So children from non-motivated backgrounds can actually re-invent themselves in school, with the right support.
My cousin's children are in a school typified by rural deprivation and isolation, and they do not have the mix of kids within which they can find any inspiration, and it is pretty dire. Idyllic area though..... The sort of place people would love to move to escape London madness.
And then there is the significant pupil premium, which at a high critical mass in many London schools may actually be making a difference. As it should.