Outcome	Number of studies	Overview of effect by study	Comparison used in each study	Effect direction per study (positive ▲; negative ▼; no change/mixed effects/conflicting findings ◀▶)
Outcome category: transmission‐related outcomes
Number or proportion of cases	1 modelling study (Naimark 2020)	Naimark 2020: the study assesses the effect of multiple interventions on the cumulative number of confirmed COVID‐19 cases after 2 months. The measures are: i) reducing the number of students (primary and elementary class sizes were capped at 23, and high school classes were capped at 15 students); ii) reduction of contacts (students remained in their assigned classrooms for the school day rather than moving among classrooms); iii) universal masking; iv) alternating attendance schedules in high schools; and v) if more than two confirmed cases of COVID‐19 occurred in a daycare or classroom less than two weeks apart, the daycare or classroom was closed for 14 days with the children in the class excluded from school rather than moved to another classroom. These measures were implemented alongside community‐based interventions. With no community‐based interventions being implemented, the cumulative number of confirmed COVID‐19 cases after 2 months with schools opening without co‐interventions in place would be 82,379 if schools are closed and 86,507 when schools are open. With community‐based interventions being implemented, the cumulative number of confirmed COVID‐19 cases after 2 months with schools opening without co‐interventions in place would be 45,112 if schools are closed and 45,068 when schools are open. The study found a large impact of co‐interventions: The mean difference in cumulative COVID‐19 cases by 31 October 2020, for the scenarios in which community‐based co‐interventions were not implemented versus scenarios in which they were implemented was 39,355 cases. In contrast, the mean difference in cumulative COVID‐19 cases for the scenarios in which schools were reopened versus scenarios in which they were not was 2040 cases.	School closure	Negative ▼