This election factsheet highlights the following points: (1) It isn't always possible to say with certainty from looking at a country's rank in the PISA educational league tables alone whether one country or economy has definitely performed better than another; (2) England's position in the league tables is dependent on which countries and economies participate in a given year and whether the performance of these countries and economies is better, worse, or the same as in the last round of PISA; (3) England has maintained the same level of performance in maths in the last three rounds of PISA (2006, 2009, and 2012). England's relative position compared to the number of higher performing countries and economies has remained relatively stable over time, although some countries have overtaken England, and are now performing significantly better; and (4) PISA data alone doesn't tell us why some countries and economies are higher achieving, why some pupils perform better than others, or which teaching practices result in higher performance. The Programme for International Student Assessment (PISA) is a survey of the educational achievement of 15-year-olds developed by the Organisation for Economic Co-operation and Development (OECD). PISA assesses students' maths, science, and reading skills. 15-year-olds from across the world take tests in the three key subjects, with a focus on one subject in each year of the assessment. In PISA 2012, the main subject was maths, and in the next PISA survey in 2015, the focus will be on science. All four countries of the UK participated in PISA 2012. This briefing document focuses on England. Where relevant, the briefing also references the findings for the whole of the UK. This piece sets out to explore how PISA results can be used to judge the success of education systems, particularly in terms of the claims that are made about PISA findings by politicians and the media.