As a teacher, I support secondary schools going online for the first couple of weeks, except to vulnerable and key worker children. I'd then support a half-in, half-out rota system where different year groups are in every other week, keeping them in their bubbles but reducing contact at school.
Schools are vital for children's education, mental health, physical exertion, social skills and for their parents' or guardians' ability to work, whether from home or not, but even with the greatest care going into risk assessments and bubbling at school, children do not socially distance.
We spend the time in between classes constantly telling children to stay apart, stop touching each other, wear masks properly etc but even after months of reinforcement, positive cases among staff and pupils and numerous self isolations, the virus is a joke to a good number of students, and these are just extra rules to rebel against.
As important as schools are, we need to do something to limit the spread before the NHS gets overwhelmed. As much as colleagues want to be back in the classroom (many of us having worked over the holidays, and who will be going into school full time even just to teach online), I'd rather this for a short period than have outbreaks interrupt a greater chunk of children's learning, or not to have this under greater control by the time of the assessments.
Above all, it's exam years' learning that needs to be prioritised during this time.