I'm early-mid 30s and when I was choosing A Levels it was expected that those with good GCSE results would do 4 A Levels, but there was no expectation that you'd drop 1 in the second year.
This was back when it was an AS Level in one year and the second year counted as your full A Level. If you did well at GCSEs but not amazingly well you did 3 A Levels.
It seems now (and I agree with this approach) that you start with 3 or 4 but if the latter you'd usually drop one at the end of the first year?
Further maths at the time (whether a widespread view or just my school) wasn't classed as a full subject, you'd do 3 A Levels plus further maths, rather than 3 including FM which seems to be an accepted option now.