Lots of things were mandatory at the school I went to that were not elsewhere, such as 3 years of Latin, 3 years music, 3 years arts, 3 years home ecc/ woodwork/ metalwork, 7 years French, and in addition to that you had to take another foreign language. The others that were also mandatory were English language, English literature, maths & I'm certain something else was but can't quite remember now (sports, swimming which wasn't on the sports category, go without saying). Over half of my 6th form year (so last exams before university) went to either Oxford or Cambridge and sitting 4 A levels was the standard, with 5 not uncommon. I studied for 5. It was common to take 9 or 10 GCSEs (so exams at 16 years old) or 9 GCSEs and additional Maths which is what I did, so you'd take Maths GCSE a year early and then go on to take a further maths exam the following year. That was the only route available you take a further Maths A level and to do maths at university. It was also expected of you if you wanted to study any of the sciences at A level and then degree (which is my background, a chemistry degree, totally and utterly unused! )