It's completely futile to think we can stop Covid spreading through schools in the longer term. Who are we trying to kid? We may be angry that we are in this situation, but we are and we have to live with it.
It seems to be that it will be far better all round if Covid is just treated as we would the flu in schools. From September all teachers and CEV pupils should have been vaccinated, so we may as well just let it happen, with children off school when they are too unwell to attend. At least that way, disruption will be minimised and concentrated into a few weeks at the start of term.