Weve got loads of schools shut near us, but have only had 1 pupil case and 1 teacher case in primary (plus one scare but was fine) and about 7 cases in secondary. The school were asked why they weren't closed when other local ones were and they said it was because it wasn't spreading through our school, rather that those few pupils who tested positive has caught it from people outside of school. I'm pretty happy that at the moment they seem to be controlling it in both schools and we don't really see anyone else.
As for bubbles, we don't see much of anyone over Christmas anyway, BIL would usually drop presents off Christmas eve and stay to play a couple of board games. So my mum will be coming to drop off presents and we will have a visit in the garden, then dh will take presents to his mums and have a cup of tea, and that'll be it for us. My mum works in the NHS so she has still been working, and MIL will bubble with BIL and SIL who will not stick to the rules, so we won't mix any more than necessary.