The people at most danger in schools are probably the teaching assistants, who work closely with younger and special needs children. Sometimes those children need physical contact, either to reassure them or restrain them.
You can't put up a perspex screen between a TA and a child.
In my experience, many teaching assistants are middle-aged and some have health conditions, which is why some have left other better-paid jobs (some teaching assistants are actually qualified teachers).
I doubt if there will be any special arrangements for staff in known high risk groups. Without them, some staff will get seriously ill and, sadly, some will die. Some pupils will also take infection back to their families.
I wish people would get real and stop coming out with the mantra that schools must go back. Yes, everybody knows that, which is why the government needs to recognise the risks and provide funding for reduction of risk. It's been the same story right from the beginning - take it on the chin, shake hands with COVID-19 sufferers, positive British attitude will get us through. Absolute b****!