Generally, students HAVE to do GCSE's in: English Language, Mathematics, some kind of Science and one foreign modern language such as French, German or Spanish.
Optionally, students will take some extra subjects, including English Literature, Statistics, Geography, History, Drama, Art, ICT, Music, Double Award Science or if you're smart enough and got a Level 6 in the SATS in science; Triple Award Science (if you pick neither double or triple science, your school will instead force you to do singular Core Science).
The GCSE's are completed in a series of exams (the finals being set in June of Year 11) and coursework, which will be a lifesaver if you're not so good at exams.
Your GCSE's are really a foundation qualification, and it determines what the student generally does next.
Shane on the other hand didn't do quite as well, getting loads of D's and 2-3 C's in Maths/English/Science, however, he has gone to college and is learning a trade in a vocational course to become a plummer, because he's not very academic.
Bob the school chav and bully and "cool kid" skipped his GCSE exams, and never bothered doing most his coursework, so he could not get into a college or sixth form, he now just sits at home smoking weed, while making somewhat of an attempt to find a job and apply to do his GCSE's again at college next year, although his 15 year old girlfriend is pregnant.
Most 14-16 year olds will either disregard their educational obligations completely, or stress themselves out so much that they are incapable of enjoying the supposedly 'best years' of their lives.
I have the good fortune to be one of the blessed people who trudge along, painfully completing coursework and grudgingly sit mock exams - and still manage to have some sort of a life.
person002: nope sorry i got GCSE coursework/revision
person001: have you ever NOT had a constant stream of overdue coursework/revision in the last 2 years?
person001: nope, and for years to come.