Ggirl sorry ds's next steps aren't working out as easily as you would want. Hoping his interview helps in the process!
Bluebell for my DS cohort has meant a lot. He has just finished his A levels at a none selective state school. His further maths class have been incredibly bright and have really spurred each other on. At least 8 of them off to Oxbridge, 14 of the year group off to Oxbridge in total, and 12 of them got all A* at A level. I think ds would still have applied to Cambridge and got his results without his cohort, but, having a bunch of mates who want to study and gee each other on and celebrate each others' successes meant it was ok to work, and ok to do well, and frankly be ok to be a nerd and a geek.
All that said, it sounds like he has a good bunch of friends, and he should, with the ability he has shown thus far, do well anywhere. 🙂