When I was growing up, my area had X 6th Form College and X College of Further Education. Two separate organisations. All the school 6th forms had shut a year or so before I started secondary so everyone went to either of these colleges. One was for A Levels and one for vocational.
I live in a totally different area now and there's one college spread across two campuses. A Levels are mostly at one campus and vocational another but some of the vocational subjects are taught at the A Level campus. My son needs to decide between two subjects each at a different campus.
There are also at least two schools I know of who have their own 6th forms, but these aren't particularly seen as better than the college, just some kids prefer the school environment. I definitely would have done. I hated college.
I don't know how the schools' 6th forms do it, or the college for A Level entry, but for the vocational courses you can enter at Level 1, 2 or 3 and that's not decided until the enrolment day which is after the GCSE results come out. But you apply for as many courses as you want before that, get an unconditional offer on them all, then make a firm choice on enrolment day and your GCSE grades determine what level you're put in.
At the beginning of the year I was hopeful my son would start on at least a Level 2 course but now most of his predicted grades have come right down from 4s in Year 10 to 1s after his recent mocks so now I'm assuming he'll start college on a Level 1 course. But then he hopefully won't find that too difficult, which is how he's found school every day of his life.
But at least it's fairly clear for him and he doesn't have to worry about certain grades for a certain course. His brother in the year below at the minute wants to do A Levels at his school 6th form. I don't think A Levels are the right path for him really but if he wants to do them he'll have to really push himself as at the minute I think he's predicted mostly 5s with a few 4s but I've tried to gently suggest that he'll find the courses too difficult if he can't get at least a 6 in the subjects he wants at GCSE.