Poor air quality has been shown to harm the health and development of children. Research on these relationships has focused almost exclusively on the effects of human-made pollutants, and has not fully distinguished between contemporaneous and long-run effects. This paper contributes on both of these fronts. Merging data on plant pollen, human-made pollutants and ECLS-K data on academic skills, I study the relationship between poor air quality in the first years of life on school-readiness, and the effects of ambient air quality on achievement of young children. I find evidence that exposure in early childhood affects school readiness at the start of kindergarten, and that the effects of air quality on the growth of cognitive skills in math and reading continue into elementary school.