Dr Harries did a MN webchat recently.
She said frequently that schools would be closely monitored (and advice updated when required)l She didn't say there was no transmission between DC or from DC to adults, just that risks were low when community transmission is low.
Of course schools have not been open during the time that community transmission was wrestled down from worrying increase, through flattened peak, to low numbers. So the bottom line has to be that we simply do not kniw the role they will play
Evidence from overs as can be useful, but there are limits to how far it can be read directly across to society here (with all the different norms for teen socialising, what the school run is like, clubs, activities and all parts of social and home life).
How teens hang out with their classmates outside school might be as much a factor as what happens in school, and if course if it's Ok to be indoors in a classroom, why would they think they should not hang out together after school?
None of the evidence base rules out transmission from children. Some say it is low, others don't. Which horse the safer bet, in terms of the consequences if it loses?