Modeling assumption for the quanta generation rate.

The quanta generation rates q are derived using the approach of Buonanno et al., which predicts q from sputum viral load. Viral loads and conversion factors for SARS-CoV-2 and Mtb are taken from Table 1 in Mikszewski et al. [33]. The droplet emission rates were recalculated based on values reported by Mikszewski et al. using the inhalation rate of a sitting person [39] for all activity levels. The activity-specific quanta generation rates were weighted by the proportion of time each activity occurs in the classroom. Three scenarios were considered: low (70% breathing, 25% speaking, 5% loud speaking), medium (50% breathing, 40% speaking, 10% loud speaking), and high activity (30% breathing, 50% speaking, 20% loud speaking).