Socioeconomic differences in the long-term effects of teacher absence on student outcomes.

School teachers' sickness absence has been shown to affect student achievement in the short run. However, we know little about whether socioeconomic backgrounds may compensate for reductions in instructional quality and to what extent teacher absence effects persist over time. This paper examines the socioeconomic differences in the short- and long-term effects of teacher absence. We use population-wide Norwegian register data to study the effects of certified teacher absence during lower secondary school (grades 8-10) on non-completion of upper secondary education by age 21 (i.e. school dropout) as well as academic achievement in 10th grade. In a school fixed effects model, we find that an increase in teacher absence of 5 percentage points reduces students' examination grades by 2.3% of a standard deviation and increases the dropout probability by 0.6 percentage points. However, the teacher absence effects vary considerably by family background, with large effects for low-SES students driving the overall effects. Overall, our findings indicate that reductions in instructional quality increase social inequality in long-term educational outcomes. This result highlights that studying heterogeneous impacts of contextual exposures is needed to understand the role of schools in shaping inequality.