The Programme for International Student Assessment (PISA) is an important international study of 15-year-olds' academic achievement. Although PISA has traditionally been used to draw comparisons across countries, there is growing interest in the production of regional (i.e. city, state, or provincial level) results. In this paper we present the first attempt to benchmark London in the PISA rankings. Pooling data across the 2009 and 2012 survey waves, we estimated a 95 per cent confidence interval for London's mathematics, reading, and science PISA scores. These are compared not only to country-level averages, but also to the scores of other major world cities and states. The paper concludes by discussing how these results should be interpreted, and possible directions for future research.