"If in September the Covid-19 situation throughout Britain is no different to the situation as of present would you propose that the schools remain closed indefinitely?"
I would hope that by then there would be Government plans and - most importantly - Government money available for putting in place :-
construction alterations (a chance for the construction industry to get contracts) that would give twice as many separate rooms, all with individual toilet and washing facilities and storage for pupils' outerwear and belongings and access to the outside without sharing corridors
a pooling of all the experience which had been gained by the various schools and education authorities around the country while they have been working both in schools with the children of key workers and online supplying, supervising and marking (!!!) educational materials for children at home
seminars where those combined skills and researches can be widely disseminated to those at the chalkface
a recruiting drive for more staff to teach and/or suprvise all the extra groups
training or retraining for the extra staff that had been recruited, including in how to implement the information that had been accumulated about effective ways of managing children ( children not adults) in an extended emergency situation
national re-awareness of the importance of distancing and segregation in a pandemic, and of hygeine measures, to an extent that no-one thinks that it is OK to risk getting a highly infectious disease unnecessarily, under the pretext of "I'm fit and healthy, I'll take my chances" when they really should be thinking of other people sharing their choice of risk with them.
All this takes joined-up thinking, which doesn't seem to be a feature of our current government.
What do you think animals think about sharing the planet with humans
High CO2 levels in classrooms are a silent barrier to learning
would be able to do that.