2022 Yes https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2789005 Giardina, John North America Modeling Teachers Staff Students Middle/Jr High (6-8) Ventilation rates COVID rates With student vaccination coverage of 70% or less and moderate assumptions about mitigation effectiveness (eg, masking), mitigation could only be reduced when local case incidence was 14 or fewer cases per 100?000 residents per day to keep the mean additional cases associated with reducing mitigation to 5 or fewer cases per month. To keep the probability of any in-school transmission to less than 50% per month, the local case incidence would have to be 4 or fewer cases per 100?000 residents per day.