Coronavirus.
Examples of indoor, enclosed spaces in America where community spread into 50% to 100% of the occupants on a given night has taken place.
Note the size of the spaces in the photos. One can think of a school building as being comprised of many small bars and restaurants.
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Countries that have done reasonably well at this waited till their new case numbers dropped below problematic level prior to opening their schools for in person classes. Many of those schools conducted outdoor classes.
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Let outcomes be the judge and jury of your work.