@WombatChocolate
I think whilst you note that people are failing to recognise their experience from the wider picture, you are failing to distinguish between sixth form colleges, tertiary colleges and general FE colleges. They are very different beasts and cannot be lumped together under "colleges" as you have done.
Back in 2010, there was a big study on the effectiveness of sixth form study, and the study concluded that sixth form colleges were the most effective, followed by schools, followed by FE colleges. And this was true for the brightest students.
"The type of institution seems to matter most for higher achieving pupils taking A-levels: When we look separately at higher ability students, sixth form colleges add more value at A level than school sixth forms, which in turn add more value than general FE colleges. For higher achieving pupils taking A levels only, 6th form colleges add around 90 additional QCDA points at A level as compared to schools, whilst FE colleges add 67 fewer points than schools." (1)
This study replicates other data going back to the 90s, but again, some thoughts as to the reasons are:
"Sixth form colleges have proven to be very successful in preparing students for higher education and the world of work. Indeed, there is research to show that students at sixth form colleges are more likely to achieve top grades at A-level than those who stay on at school. This may be due in part to the fact that sixth form colleges employ teachers that specialise in A-level provision and have more experience working with students in the 16-18 age bracket." (2)
And indeed, more research has shown smaller sixth forms to be less effective in teaching students. (3)
Having taught in the past few years in an FE College, a school with a small struggling sixth form, an OFSTED outstanding school (in all categories) with very large sixth form (600+ students) and now in a sixth form college, I would agree with the points in 2. I would say of the staff I am with now, those in 6FC are the most academic I have worked with (almost all have masters or doctorates), they are subject specialists and they are devoted to A level teaching. No conflict of interests with lower school requirements.
So I don't think you can say schools are better, the evidence suggests otherwise. However, given the small number of 6FC (there's about 50 in the national association of 6FC) the numbers of them going on to HE etc will be skewed. Students at 6FC are less likely to be working class, whereas students in FE are more likely to be working class, so hard to make generalisations about progression.
(1) - cee.lse.ac.uk/ceedps/ceedp124.pdf
(2) www.educatemagazine.com/sixth-form-a-stepping-stone-to-success/
(3) www.thetimes.co.uk/article/big-sixth-forms-get-better-results-with-less-money-study-finds-jlmzl0fbt