Critics of education reforms in England argue they are socially and academically divisive because some groups of pupils are more able to exercise choice than others. This paper looks at the transitions made by pupils from state-funded primary to secondary schools in London in 2008. It examines the flows from the one to the other, determining which secondary schools recruit from the same feeder primary schools and which may be said to be competing. Using a measure of ‘best in class’, evidence is found of higher and lower attaining pupils separating from each other with the former more likely to be enrolled in selective schools (unsurprisingly given they set entrance examinations) and also some types of faith school (which do not). The separations are evident between locally competing schools but with no evidence they are worsening over the period 2003 to 2008. This apparent inertia suggests the paradox of promoting school choice within a system that imposes geographical constraints upon that choice and may, as a result, simply reinforce existing social divisions.