DD (12) has actually made it until now without getting a self-isolation contact from school, but it's just happened. DH thinks maybe she should be mostly staying in her room for the duration, I think for contact self-isolation there's no need to go that far unless she develops symptoms - though she should wash hands more, not share towels and obviously not share food and drink.
I got the impression that staying in your room was only if you have symptoms/a positive test.
We've got a fairly spacious house, so she could just hang out on the daybed in the front room (which we don't use as much as it's awaiting redecoration in the new year) rather than the lounge to lower contact a bit as well.