A recent publication by MIT's departments of chemical engineering and mathematics cited that the current "Six-Foot Rule" as recommended by the CDC offers little protection in indoor spaces. I think this information is being taken out of context because the whole article needs to be factored. More specifically, particle size matters. The six-foot guidelines are more specific to a certain size of droplet. I did my best to summarize and clarify some key points to the research including: respiration rates in relation to activities AND general health and obesity, types of AC filtration, classroom risk based on expiration types, outflow air rates, etc. Here's the full article: https://www.pnas.org/content/118/17/e2018995118#disp-formula-6