We estimate the effect of class size on student performance in 18 countries, combining school fixed effects and instrumental variables to identify random class-size variation between two adjacent grades within individual schools. Conventional estimates of class-size effects are shown to be...

This paper exploits discontinuous grade mixing rules in Norwegian junior high schools to estimate how classroom grade composition affects pupil achievement. Pupils in mixed grade classrooms are found to outperform pupils in single grade classrooms on high stake central exit tests and teacher set...

We employ a combination of school fixed effects and IV estimation to estimate the effect of class size on student performance in 18 countries. Using the random part of the class-size variation between two adjacent grades within individual schools allows us to identify causal class-size effects....