From the Executive Summary: "Many kindergarten through 12th grade (K-12) schools in the United States do not have good ventilation. This is a longstanding problem with demonstrably negative effects on student learning. We can and should act to fix this to ensure good indoor air quality for all students, educators, and school staff. During the COVID-19 [coronavirus disease 2019] pandemic, it is even more important that ventilation problems in K-12 schools be addressed now. Along with other mitigation measures, improvements in ventilation in K-12 schools can decrease the risk of SARS-CoV-2 [severe acute respiratory syndrome coronavirus 2] spread."
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Johns Hopkins Center for Health Security: https://www.centerforhealthsecurity.org/