I wonder then why many countries enforce them in open spaces. Note, this meant as a honest question.
> We still don't have the data but I think a large part of infections is happening at home were prophylactic measures are highly impractical and impossible to enforce.
Some research on current evidence was published in Science last month[1]. With the exception of some specific "job related" events (like meat packing plants) or public gatherings, most of the transmission is in fact in the household.
> the assumption being that students are acting as silent spreaders (due to the low morbidity in young people), reaches home and multiplies easily there.
I've seen this a few times, but as far as I can see the current data are absolutely inconsistent. And the largest contact tracing study from India (recently published) was done with closed schools, so no information from there either.
[1] https://science.sciencemag.org/content/early/2020/09/29/scie...