Published in: Economic Journal 126 (593). (2016). 1164-1192. (with Marte Rønning)
To estimate the impact of grade composition on pupil achievement we exploit grade mixing rules in Norwegian junior high schools in an instrumental variable framework. We find that pupils in mixed grade classrooms outperform pupils in single grade classrooms on high stake central exit tests and teacher set and graded tests. This effect is driven by pupils benefiting from sharing the classroom with more mature peers from higher grades. We also find that the presence of lower grade peers is detrimental for achievement. Children can therefore benefit from de-tracking by grade, but the effects depend crucially on how the classroom is balanced in terms of lower and higher grades.