Palacios, Eichholtz, Kok and Duran:
Governments devote a large share of public budgets to construct, repair, and modernize school facilities. However, evidence on whether investments in the physical state of schools translate into better student outcomes is scant. In this study, we report the results of a large field study on the implications of poor air quality inside classrooms − a key performance measure of school mechanical ventilation systems. We continuously monitor the air quality (i.e., CO2), together with a rich set of indoor environmental parameters in 216 classrooms in the Netherlands. We link indoor air quality conditions to the outcomes on semi-annual nationally standardized tests of 5,500 children, during a period of five school terms (from 2018 to 2020). Using a fixed-effects strategy, relying on within-pupil changes in air quality conditions and test results, we document that exposure to poor indoor air quality during the school term preceding a test is associated with significantly lower test results: a one standard deviation increase in the school-term average daily peak of CO2 leads to a 0.11 standard deviation decrease in subsequent test scores. The estimates based on plausibly exogenous variation driven by mechanical ventilation system breakdown events confirm the robustness of the results. Our results add to the ongoing debate on the determinants of student human capital accumulation, highlighting the role of school infrastructure in shaping learning outcomes.