Résumé
This paper estimates the causal effects of math instructional time on student achievement using within-student variation across math topics in the TIMSS 2011 data. Based on the assessment’s detailed measurement of math skills, it shows that each weekly hour of math instruction increases student test scores by 4.3% of a SD. However, the productivity of instructional time varies significantly based on the implementation of teaching practices that prioritize student active participation: teachers emphasizing these practices are more than twice as productive as other teachers. This result holds true regardless of student gender, social origin, and is observed internationally in 42 countries.