International tests demonstrate that students' mathematics and reading skills vary widely across countries. I investigate whether a country's cultural characteristics are the fundamental cause of these differences, while family and school characteristics are the proximate causes. I find that while either cultural characteristics or family and school characteristics can explain average student scores on PISA mathematics and reading literacy tests across countries, when the effects of both types of characteristics are examined together, the cultural characteristics explain most of the differences. These results indicate that families and schools function as agents of society and that schools have a limited capability to improve students' skills absent accompanying changes in a country's cultural characteristics.