Schools are huge hotspots in my experience, although secondaries are much riskier due to the sheer volume of kids and the fact they mix frequently due to subject choices etc.
Primary is easier to control and keep in bubbles BUT it depends on the school setup. A primary that has separate infant and junior facilities eg two yards/halls will be easier to separate than those without.
My fear is that closing everything BUT schools won't slow the spread enough and we'll have to do all this again for longer, risking even more businesses and jobs in the process. Surely even just closing secondaries would help and there would be fewer childcare issues. Realistically though many parents face issues regardless due to needing to isolate the entire family for every cough, if bubbles burst etc.
There are schools locally where whole years, or large chunks of them at least, have had to isolate 2-3 times already. This puts attendance at around 50% at best for many. Also, since the teachers are still teaching those in school, online learning at these times is minimal with just tasks/worksheets at best so many kids are missing massive chunks of learning.
Surely there has to be a better way? In England, they are even refusing to cancel or adapt GCSEs/A Levels and as such year 11/13 kids are really suffering due to having to try and cram in all the work they missed over lockdown plus continually catching up on work after isolation. Their mental health is deteriorating rapidly and they are being utterly failed.