Have isolated with a 14, 13 and 10 year old (who has special needs)
We stayed in, only going into the garden, as the rules state.
Ds has had a period of self isolation of 10 days, the dds had a period of self isolation of 4 days, and we have all self isolated as a family twice (once for 8 days, once for 14 days)
To be honest ds is medically vulnerable, so from March to August we stayed in. Dh worked - outdoors, completely socially distanced, the dds shielded with ds, going for walks and bike rides together towards the end of the shielding period, but ds didn't go anywhere.
A friend whose DC are at a posh London school wern't told their DC had to stay indoors. I guess you get what you pay for.
Your friend's dc's school are wrong, the very posh school near us, are complying 100% with the guidelines.