Good or Bad? Short- versus Long-Term Effects of Multigrading on Child Achievement

This paper studies the effect of multigrading—mixing children of differentages in the same classroom—on students’ short- versus long-term academicachievement in Italy. We cope with the endogeneity of multigrading (andclass size) through an instrumental variable identification strategy based ona law that disciplines class composition. By relying on longitudinal data thatfollow a cohort of Italian students over their compulsory school career, weshow that multigrading has a positive short-term effect on achievements.This effect fades away over time to become negative in the long run if studentsspend several years in a multigrade class. The analysis of mechanismspoints to the fundamental role of teachers and suggests that no negativelong-term effect arises when multigrade classes are taught by more experiencedand motivated teachers. These results reconcile contrasting findingsin the literature based on cross-sectional data and a short-term focus