The limited impact of extending the school week on educational outcomes in Dutch primary education: a quasi-experimental study using penalized synthetic control analysis

This study uses a quasi-experimental design to investigate the causal impact of an extended school week on educational performance in 22 Dutch primary schools. The intervention has been partly modeled after the prominent Harlem Children’s Zone (HCZ). To assess the impact of the intervention, we leverage register data containing information on all Dutch children finishing primary school in the period 2009 - 2022. Synthetic control analysis is applied to estimate the causal effect for each individual school. The findings show the program has had limited effect on educational outcomes with little variation between schools. Our contribution is in showing how several factors, such as goal switching, lack of participation, and teacher shortages, hamper program effectiveness and discussing to what extent a concept such as the HCZ is transferable to other international contexts. Finally, we also illustrate how the synthetic control method can be applied in educational research.