Nature Sustainability

Approximately 25 million children ride buses to school in the United States. While school buses are the safest school transport from an accident perspective, older buses often expose students to high levels of diesel exhaust. Because these exposures can adversely impact health, which may lead to more missed school, the US Environmental Protection Agency (EPA) has spent millions of dollars to hasten the transition of school bus fleets to cleaner vehicles. Here, we leveraged the randomized allocation of the EPA’s 2012–2017 School Bus Rebate Program funding to causally assess the district attendance impacts of upgrading buses. Districts randomly selected for funding had greater attendance improvements after the lottery than unselected districts, resulting in over 350,000 estimated additional student days of attendance each year (95% confidence interval = −70,678 to 772,865) due to the use of EPA funds.