How does Instruction Time Affect Student Achievement? The Moderating Role of Teacher Qualifications

This study focuses on the interaction between the quantity and the quality of instruction at school. On average, across all studied countries, one hour more instruction time leads to 0.03 standard deviations higher test scores. Importantly, the effect varies according to teachers' formal qualifications: It is larger for students with better qualified teachers. The moderating role of teacher quality is particularly important in understanding the effect of instruction time in developing countries: more instruction time alone has no significant effect on average in these countries, but instruction by a highly qualified teacher increases test scores by 0.02 standard deviations.