@cornishdreams1 I have never seen a school which regularly teaches students in groups of 45, except for PE. If this was happening regularly, it would be a national scandal. I trained in some inner city schools, and never saw this happening. I known people who teach in London, and this doesn't happen there, either.
I could not teach my subject (science) safely to a group of 45 students (the actual advice is groups of no more than 26 for practical work, I believe, although of course this is ignored).
45 students crammed into a small classroom is also a transmission risk- they may not get very ill (although some secondary age students will) but they can take it home to their families and make their parents ill.
I am not saying it can't be done- but it would just be a holding facility for children if you are talking about class sizes that large, and who does that actually benefit? In primary it may benefit parents as there will be some childcare, but I would argue this doesn't benefit children in any way, and actually puts them at risk.
If we are talking about schools going back as childcare, then to me the priority is actually opening from the youngest age groups up with whatever teachers are available- secondary or primary. This is fine if it's what the country needs to run, but then let's be honest about it.
FWIW I care deeply about my students, but my first concern is that we minimize the number of students who lose family members due to this AND the number of students who die (for the 11-19 age group, this number is not 0 from the Chinese data).