Using rich longitudinal data from the UK's Millennium Cohort Study (MCS), the authors compare the performance of private and state school pupils in age 16 national examinations (GCSEs) in England, where private schools are particularly well resourced by international standards. Performance among pupils attending private secondary schools is superior. However, this raw difference ignores the highly socially selective nature of the English private school system. Adjusting for socioeconomic background, the overall performance difference between the sectors disappears. The picture is also quite different when considering English, Maths, Science and Arts subjects separately. Implications are reviewed for debate surrounding the role of private schools and the emphasis of lower secondary state education on core subjects at the expense of Arts subjects.