Many U.S. schools were in dire need of upgrades — burdened by leaking pipes, mold, and antiquated heating systems — long before the covid-19 pandemic drew attention to the importance of indoor ventilation in reducing the spread of infectious disease. The average U.S. school building is 50 years old, and many schools date back more than a century. So, one might assume school districts across the nation would welcome the opportunity created by billions of dollars in federal covid-relief money available to upgrade heating and air-conditioning systems and improve air quality and filtration in K-12…