Market-based reforms of state schooling systems have been justified by the benefits anticipated from encouraging greater inter-school competition in local schooling markets. Promoting increased school choice and competition by comparison were seen as a means of stimulating greater allocative, productive and dynamic efficiency in the schooling system. However in England, school effectiveness research suggests that once adjustment is made for pupil characteristics, variations in pupil attainment levels between secondary schools are small and unstable over time. Some evidence suggests that differences in pupil attainment by subject within schools are larger, indicating the potential to raise attainment levels by increasing choice within schools. In this paper we seek to extend the school choice debate by examining the rationale for increasing competition within secondary schools.