I agree with @roycroftmom . UK colleges are very much sink or swim. I have a lot of British nieces and nephews. They were always surprised at how far American students lagged behind. UK students start their majors immediately. It’s not a great system for students who might need a little longer to get motivated.
I’m not trying to be rude, but even if your son is super smart, it won’t be as important as him being willing to do the work. So don’t force him.
My son is dyslexic and dysgraphic. He is smart but much lazier than my daughter, and, of course, struggles more. For the most part, high school was about maintaining a balance between not letting him coast and and not stressing him out. And when he was a sophomore, I pushed too hard. I insisted he take Honors Chem. It was a disaster. The teacher was really hard. He moved down to regular chem, and had to take the C with him. He ultimately earned an A in regular chem, and it worked out, but I regret that I pushed too hard and caused him a lot of stress.