I think it is really important to understand your dc’s learning style and strengths. So for DC2, he is a straightforward academic learner, he really enjoyed one a level (politics), knew he wanted to do it at uni, and it has been a good choice for him. BUT although on paper he looked like an obvious oxbridge applicant, he knew that he did not cope well under extreme pressure of deadlines (has ADD) and the reduced terms and workload of oxbridge wouldn’t work for him. So he went to another RG and has gone on a year abroad and huge success with firsts every year so far.
DC1 however - she is dyslexic, full extra time, very bright/high iq but severe processing difficulties mean even with extra time exams are awful for her. She started looking at geography degrees and I was thinking “I just can’t see her sitting in lecture theatres and libraries cramming for timed exams”. One uni sent an email to all those who registered for geography open day an email saying “have you thought about landscape architecture?”. And that just clicked. So we went to look - best dept in uk (arguably Europe), creative but rigorous, lots of practical fieldwork, no exams, all assessed coursework which is done at own speed - she loved it. 2.1 from RG, also did Erasmus semester abroad - got a job, did masters part time, then professional exams - if you told me at 16 she would be professionally qualified at 24 earning 60k+ I would have laughed in your face.
so think creatively. DC3 is like DC1 but scientific so has chosen a very hands on oceanography course with lots of coursework and fieldwork and only 10% times exams in the degree. I am sure he will do well. You have to match the kid’s strengths, learning style and interests with the course and the uni. That requires a lot of research and a bit of luck for some kids. Others could go pretty much anywhere and do anything.