Everyone has been told they don't have to send their kids back if they don't want to, so YANBU. From polls I've seen, about half of parents will not send their kids back so, there is your problem solved regarding classroom capacity.
I fully appreciate the HT's passionate reaction and I do think the Government could have done a much better job selling this new approach. Dumping the news on everyone just before bedtime was bound to cause stress and confusion.
I do think there needs to be a much more orderly, planned and documented approach to getting schools back. They should have done some simulations in real schools, and published notes to schools explaining how to handle staffing issues, whether to have a week on/week off model, what to do about lunchtimes, what to do about drop off and pick up (if you stagger it,.parents with kids in different years will have to hang around which could be dangerous as people will cluster together), what to do if a child gets I'll- fo you close the school or the child's class and do you inform the parents etx.
There is a huge amount of detail missing and it is INSANE to expect schools to develop this detail themselves, and unfair to tell schools to prepare to go back to new normal without letting schools know how and when they will receive clear advice and instructions regaring best practice policies and "showstoppers" which need special help.
I think it has been handled very badly by the government.
It makes me very fearful about Brexit, as the Government simply isnt competent.