Again, people seem to be missing the point, that despite lots of clever people (measured by GCSE results for simple measurable data, A Level results and where people end up at Uni) those from school sixth forms are more highly represented.
Think RG unis - lots of clever people - more from schools than colleges - factor in the 20% of the population dictated privately at 6th Form level (in schools mostly) and all the state Grammars and highly selective leafy comps sending people to RG unis, then you can see this is reality.
Its not to say that clever people don’t go to college too, or that in some areas, all the clever people don’t go to college - because there aren’t any 6th forms in schools or only a tiny number, or that there aren’t lots on MN or their kids who are clever and went to college. But nationally, if you think of those with grades 7-9 at GCSE as being the clever ones, you’ll find many are in schools. Colleges have their share if them too, but given most schools focus mostly on A Levels, those who don’t do A Levels by default are more likely to go to college. Therefore the majority of those who do t achieve grades suitable for A Level go to college. With higher ability it is more mixed - yes some go to college, but lots remain in schools too.
The mire academic the Uni, the higher proportion of kids from schools rather than colleges you’ll find.
Its no criticism of colleges nor suggestion that those doing A Levels at college can’t do really well or are limited in any way. It’s simply a fact that whilst those doing A Levels have a choice of 2 places to study - school or college, those doing vocational usually just have college.