A number of studies have explored the link between family background and children's achievement in a cross-national context. A common finding is that there is a stronger association in England than in other parts of the developed world. Rather less attention has been paid, however, to England's comparative position at different points of the achievement distribution. Is the test score gap particularly big between the most able children from advantaged and disadvantaged homes, or are differences particularly pronounced between low achievers? This issue is investigated using the Programme for International Student Assessment (PISA) 2009 data set. The association between family background and high achievement is found to be stronger in England than in most other developed countries, and there is little evidence that this has changed over time. However, socio-economic differences at the bottom of the achievement distribution are no more pronounced in England than elsewhere. I discuss the implications of these findings for social mobility and educational policy in the UK.