In what ways did your DC find A Levels different to their expectations

[MeanderingStar]

Currently considering choices, but interested in both general, 'how was studying for A Levels different' and specifically 'how was that subject different'. (Esp Psychology, French, Maths and Music!)
Surely they all expected to become more responsible for their own learning and for it to be harder - but what surprised them?

When GCSEs were still on letter grades, a study was done which showed that at A level, students score 1 grade lower on average than they did in the same subject at GCSE, but for maths, science and MFL it was 2 grades lower. So someone getting an A (or 7) at GCSE in maths or French would be expected to get a C in the same subject at A level, whereas someone getting a 7 in history or English literature would be expected to get a B at A level. One could argue that maths, sciences and MFL therefore have a bigger "step up" from GCSE to A level than other subjects, as measured by the average drop in grades.