Andrew Marr asked Dominic Raab a similar question today. Raab's answer, obviously not being able to go anywhere specific, amounted to they're going to have to think of ways to keep social distancing in place. Because, as he said, the issue isn't with the children - who may be very unlikely to get Covid 19 badly (according to the science at the moment).
The problem is that little Jane's dad has asymptomatic Covid, she sits next to little John who picks it up from her and takes it home to his mum - who is a key worker or to gran who he lives with.
I work in a secondary school which is a hub for key workers at the moment. We have 100 pupils from primary and secondary combined in the school at present. To socially distance we've had to have no more than 10 in each class, parents have to provide a packed lunch which the kids eat in situ.
I was saying to DH that a rough estimate for pupil places, if we kept to social distancing would be about a third in at any one time.
So normally we have 2000 pupils in our school. Divide that by an average of 25 pupils per class (allowing for some being 32 pupils, some SEN classes being just 18) and you get 80 classes taking place each day. Multiply that by 10 children per class for social distancing and you have 800 pupils in at any one time. Which means either split days or 1 week in x number in school.
And that would also help solve the issue of secondary children who travel - I wouldn't want to be the driver of a bus rammed with kids on two journeys a day, five days a week.
But if, as Raab is hinting, social distancing measures are needed in schools, you won't have 2000 kids all back at the same time.
The alternative is using different venues, like town halls, church halls, leisure centres, to take overspill classes from the 800 in our case. But you'd have to find accommodation for 1200 per week to enable us to socially distance AND have every child in school every day, every week.