When children are infected they still give off viral particles, most likely at a reduced dosage amount if asymptomatic (or mild symptoms). Teachers are probably somewhat safer if masked with N95s and keep distance and with proper air circulation. Parents are at risk since they will be very close to their children and with children leaving their nose picking stuff around the house. This is transmitted by small micro aerosols indoors definitely without airflow and dilution. Cloth masks work for the larger droplets but not the small aerosols.