Student performance can be assessed through results from the OECD Programme for International Student Assessment (PISA). PISA is the most comprehensive international effort to measure the skills of students towards the end of the period of compulsory education. In the latest results, 15-year-old students across the OECD did tests in reading, mathematics and science in 2006 (the United States is not included in the reading test). In PISA comparable tests are administered under independently supervised conditions in order to assess students’ competencies. PISA tests are not tied to specific national curricula. Rather, students apply knowledge to situations they might encounter in the real word, such as planning a route, interpreting the instructions for an electrical appliance, or taking information from a figure. For each subject the average score across OECD countries is 500 for the first time it becomes a major domain in PISA. Thereafter the OECD average reflects the performance of the OECD countries.