Clouded Minds: Air Pollution and Student Cognitive Performance

We estimate the causal effect of air pollution on primary school students' cognitive performance in Italy, exploiting daily within-municipality variation in pollution across exam dates. Using INVALSI administrative data on the universe of students over ten cohorts and a specification with individual fixed effects, we find that a 10 μg/m³ increase in PM2.5 reduces test scores by 4.4% of a standard deviation. Effects are concentrated in reasoning-intensive items, with no significant effect on knowledge-based items, are stronger for lower-achieving and emotionally vulnerable students, and are substantially mitigated by school mechanical ventilation and air-conditioning systems. These results highlight the cognitive costs of short-term pollution exposure and the potential of targeted infrastructure investments to reduce environmental inequality in education.