We re-examine the importance of instruction time for student achievement on international assessments. We successfully replicate the positive effect of weekly instruction time in the seminal paper by Lavy (Economic Journal, 125, F397-F424) in a narrow sense. Extending the analysis to other international assessments, we find effects that are consistently smaller in magnitude. We provide evidence that this discrepancy might be partly due to a different way of measuring instruction time in the data used in the original paper. Our results suggest that differences in instruction time are less important than previously thought for explaining international gaps in student achievement.We re-examine the importance of instruction time for student achievement on international assessments. We successfully replicate the positive effect of weekly instruction time in the seminal paper by Lavy (Economic Journal, 125, F397-F424) in a narrow sense. Extending the analysis to other international assessments, we find effects that are consistently smaller in magnitude. We provide evidence that this discrepancy might be partly due to a different way of measuring instruction time in the data used in the original paper. Our results suggest that differences in instruction time are less important than previously thought for explaining international gaps in student achievement.