A commenter correctly identifies the outcome.
As many as three-quarters of [British] state schools are failing to push their brightest pupils because teachers are reluctant to promote 'elitism', an Ofsted study says today.
Many teachers are not convinced of the importance of providing more challenging tasks for their gifted and talented pupils.
Bright youngsters told inspectors they were forced to ask for harder work. Others were resentful at being dragooned into 'mentoring' weaker pupils.
Until the common schools, beginning in kindergarten, stress development of the habits of the upper middle class in all their students, the social stratification will only get worse.
I'm worried about rising caste differences, but I think schools are only a small part of the problem. A diminishing number of families teach their children to dress and groom for a good first impression; speak and write coherently; show poise in formal settings; and so on.
Those who do these things, send their children on up the social scale. Those who don't, condemn their children to lives of clueless subservience. Whether they can factor polynomials or conjugate irregular verbs is pretty much beside the point.