I think a definitive calming stat would be to primary kid's parents and teachers if we knew the amount of secondary infections. Eg. School A, no infections but School A parents infections=2, teachers=3.
And just as I was typing it popped in how bad this would be. These secondary cases could have picked it up anywhere, so unless someone is purely staying home this would be useless.
There are enough families where both parents WFH and aren't really doing much else (and certainly not in contact with anyone else without SD and masks) that this would be useful. Also, SAHPs, I know at least 2 single mums that have no exposure outside of their children.
My concern about primaries is viral load - it is impossible for reception teachers to distance - they have snot and coughs directly in their face, crying kids, wiping bums, being pissed on. The only way you can get a little child to calm down sometimes is physically touching them, getting close. This is the reality of little children. For parents, they may have to sleep in with their children when ill. High viral load.
Risk assessment should be about likelihood AND severity of harm. It's why we invest large amounts in safety procedures around nuclear power plants. The chance of an accident is extremely low, but the potential harm in the very very unlikely case that it happens is very high.
I suspect that primaries won't drive transmission, but this isn't helpful to vulnerable teachers and parents who could receive a massive viral load. So we need this sort of data to assess risk properly and make decisions .
Similar robust risk assessments needed in secondary - distancing is more likely but some teachers could be potentially exposed to massive viral load just from volume of students and length of exposure.
Masks do reduce viral load of course, so that would be an obvious solution for teachers without shutting schools or investing in them.