Since its inception in 2000, the Program for International Student Assessment (PISA)1—an international test of reading, math, and science—has shown that American 15-year-olds perform more poorly, on average, than 15-year-olds in many other developed countries. This finding is generally consistent with results from another international assessment of 8th graders, the Trends in International Mathematics and Science Study (TIMSS).2
International test rankings have come to dominate how politicians and pundits judge the quality of countries’ education systems, including highly heterogeneous systems such as that of the United States. While international tests and international comparisons are not without merit, international test data are notoriously limited in their ability to shed light on why students in any country have higher or lower test scores than in another.3 Policy prescriptions based on these test results therefore risk being largely descriptive, based on correlational evidence that offers limited and less-than-convincing proof of the factors that actually drive student performance.
