Educational outcomes are shaped by a wide range of factors, including innate students’ characteristics, family and school background and other environmental factors. But a key-question for policy-makers is what schools and school policies can do to raise overall student performance. Several studies have indeed shown the positive effect of an increase in cognitive skills and competencies on both social and individual economic welfare. From a macroeconomic viewpoint, international differences in student achievement tests have been shown to increase long-run economic growth. Our analysis focuses on the quality of school systems, i.e. on the association of educational policies with average learning outcomes.