Y10 is 13-14 with 14 being the "legal" age kids can be left at home alone or in charge of younger siblings
And younger kids have one class, one teacher, which is easier to manage bubble wise. Rather than the kids having periods during the day with different teachers and pupils in each of them
Depends on the school these days - some don't work that way any more - are more open plan/mixed.
I think more data is needed. It appears that young kids not only don't get C19 symptoms, but are far less likely to get infected in the first place, and assumed from that to probably not be the feared super-spreaders that was a serious concern weeks/months ago.
I hope we don't make a serious mistake on that by making decisions based on poor data.
There's another study, this time from Holland, indicating that ~>10x as many from the general population who donated blood are C-19 sero-positive than have been diagnosed. Something weird is going on. The serology testing is either flawed - or the disease is very poorly understood, or both, as the data coming out strongly conflicts with epidemiology of the disease in countries like NZ, Aus, Korea etc - where contact tracing has been successful in reducing spread. That simply could not happen if ~90% of cases were undiagnosed and those cases were infectious/shedding virus. So either the serology test is picking up false positives perhaps because some/many people have similar antibodies from other past infections, or a lot of people get C-19 and are not getting symptoms and are not passing the infection on.