Governments devote a large share of public budgets to construct, repair and modernize school facilities. However, little is known about whether investments in the physical condition of schools translate into better student achievements. In this study, we report the results of a large field study, providing evidence on the impact of environmental quality inside classrooms on learning outcomes. Indoor environmental quality is considered a key performance measure of school infrastructure, and a common indicator guiding investments in school facilities. We employ continuous sensing technology over three school years, installed in 139 classrooms across 27 primary schools in the Netherlands, and use the Dutch standardized primary school testing system to measure learning outcomes. This allows us to investigate the relationship between different aspects of indoor environmental quality – temperature, CO2, fine particles, humidity – and the performance of almost 3,000 children between ages 6 and 12 on some 22,000 tests.
Using a fixed-effects strategy, relying on within-pupil changes in exposure to environmental conditions and test outcomes, we find significant underperformance in testing scores for children who have been chronically exposed to adverse indoor climate conditions in the semester preceding a test, with exposure to high CO2 levels being most salient. We document that indoor climate conditions at the time of testing also affect student performance, with fine particle exposure being most salient. A potential mechanism for the learning effects may be that adverse indoor climate conditions during part of the day lead to significantly longer subsequent breaks, reducing learning time in the classroom. Our results add to the ongoing debate on the determinants of student human capital accumulation, highlighting the role of physical capital in affecting learning outcomes.