I thought CoffeeHousers may have some thoughts on this passage from Davis's article, in particular:
"The hard data shows that the post-war improvement in social mobility, and its subsequent decline, coincided exactly with the arrival, and then the destruction, of the grammar school system. This is the clearest example of the unintended consequence of a purportedly egalitarian policy we have seen in modern times."
We shall have more on grammar schools, and their effect on social mobility, shortly. But to get the debate off to a start, and because I've been reading it recently, here's a short passage from Andrew Adonis's and Stephen Pollard's A Class Act that seems to support his thesis:
"Modern mythology has it that the number of privately educated children at Oxbridge is on a steadily declining path. And indeed it was — in the heyday of the state grammar schools in the 1960s. By 1969 only 38 per cent of places at Oxford were awarded to private educated children — a sharp reduction for the private schools even on their 1965 proportion. And yet in the 1990s, thanks to the destruction of the grammar schools and the consequent decamping to the private sector of many of the most able children, the figure now hovers around the 50 per cent mark."