This paper investigates whether international differences in math and science achievement, and specifically the lower US scores, can be explained by school programmatic, institutional, and resource differences after controlling for family SES factors. Using 2006 PISA student-level data for the 10 largest developed OECD countries, the results show that, while family SES has a strong impact on students’ achievement, it does not explain the US achievement gap with other developed OECD countries. In contrast, a substantial number of school variables not only have significant impacts on math and science achievement, but they contribute more to these gaps than SES differences. Of particular importance for policy purposes are the lower amounts of time devoted to studying math and science in the US, as well as student-centered pedagogical techniques which are emphasized in the US but not in such high-scoring countries such as Korea.