At my very academic direct grant school, I don't believe it was possible to do CSEs at all. We were all entered for 8 or 9 O levels, and as some girls struggled to get more than 2 or 3 passes, they were really short-changed by this policy.
Some girls did Additional Maths AO in Lower VI if they were doing Science A levels but weren't doing a Maths A level.
A girl who joined us for sixth form had previously been at a local comprehensive school. The head there had tried to remove the option to do O levels at all, on the grounds that a CSE grade 1 was just as good as an O level pass. She said there was a big pushback from parents who thought he was wrong.
Took my O levels in 1977. JMB. No coursework at all, no modules, no open book exams, all unseen exams at the end of what would now be year 11. I didn't do Art but from what I remember the girls who did spent all day in the Art room painting, a bit before the main run of exams. No science practicals. Music must have had something other than just written exams, but I didn't do that either, so don't know. Domestic Science definitely involved a practical exam. French and other Modern Languages involved not just an oral, with an external examiner, not one of our own teachers, but also a dictation exam and an aural exam (tape recording played, we had to answer questions on it).
All so long ago!