Marsha,
I can't think of a good way of managing primaries that pleases everyone - or indeed one that pleases anyone!
Isolation is a particular difficulty because they cannot isolate alone, which has an impact on parents.
Testing is more difficult on younger children, and many parents are reluctant to force their younger children to be tested.
Distancing is impossible for staff in primary schools, which are by definition more hands-on.
While bubbles are much smaller - typically 30-32 - the group is together in such close quarters for so much time each day that reducing this number by defining 'close contacts' is not feasible.
Childcare and similar structured after-school activities inevitably mix bubbles, creating more contacts.
Unless the Government is prepared to fund true mitigation measures in primaries, particularly ventilation and smaller grouping, then I do think that the only way forward will be to let it run totally out of control and be ready to treat those (probably family members and staff) who become ill.