It isn't just about children though, is it, the opening of the schools? The UK is at peak pandemic/2nd wave right now. The virus is raging. If schools open, the R rate will soar.
The R rate given on Gov.uk was 1.1 to 1.6, BUT dates 23rd Dec. Obviously, after the Christmas and New Year mixing it is much higher now.
I agree, it is awful for children. It is much worse for school staff. But it could also drive the country to breaking point. The NHS isn't coping now. Imagine what will happen if things get even worse. I fear for my family's lives.