The reason, of course, is that the interests, abilities, and ambitions one has at 14 can be very different from what may have developed at 16 or 18. So the objective at GCSE is to secure a broad and balanced educational foundation that will test interests, hone abilities and leave open as many options as possible for further studies.
In a qualifications-oriented world, it is easy to work up a fair amount of anxiety about taking enough subjects and the right subjects - and the awful possibility of irrevocably slamming doors you would prefer to leave ajar. In fact, long before the national curriculum, good schools arranged their options blocks in such a way that it was difficult to go seriously wrong.
English, maths, science, a foreign language: everyone recommended them, schools pushed them, universities wanted them. Pupils taking those subjects now, plus a subject from the humanities and from the creative/aesthetic subjects, will more than satisfy the requirements of the national curriculum. They will also have an excellent base for further studies across the board. Medicine, law, accountancy - fine. Dentistry, drama, environmental work - no problem. Engineering, management, journalism - all in the running.
So where is the choice? What are the compromises?
Problems arise largely because schools have to limit the number of GCSEs pupils take. There are other subjects that make a claim on the timetable: the national curriculum includes PE, and the law demands religious education.
Schools will have their own policies about how many GCSEs pupils normally take. Those who are likely to go on to study A-levels and university will need to aim for at least five or six. In practice, most will take more, some as many as ten.
A starting point of maths, English, science and a foreign language seems to leave plenty of choice, but it is not quite that simple. First of all, English is often two separate subjects, language and literature.
Science is perhaps the area on which your other choices turn. The national curriculum decrees that all science should be 'balanced', that is, include physics, chemistry and biology. A course which leads to one GCSE, known as 'single science', obviously leaves the greatest choice at this level but restricts it later.
'Double science' is the choice for many pupils. It equals two GCSEs, and, while it takes up an additional GCSE choice now, it is a suitable foundation for the study of the sciences at A-level and beyond and so leaves open more options later. Some schools still offer separate sciences in the belief that they are the best preparation for science high-fliers. But pupils are no longer allowed to take just chemistry and biology, or just physics and chemistry. The requirement that all science be balanced means that this option takes up three choices.
Many schools will insist on a humanities subject - and will be serving pupils' long-term interests if they do. Now that the national curriculum no longer specifies history or geography, subjects that were at risk, such as RE, business studies, and economics, could get a new lease of life.
At the end of the day, there may well be compromise and disappointment. Some pupils may not be able to take a second language. Others may face a hard choice between history, geography, economics or integrated humanities. Some may have to choose between art and music when they would like to do both.
A choice that includes English, maths, science, a foreign language, a humanities or 'social' subject, and a practical or creative subject is a broad, balanced and flexible springboard leading to a wealth of opportunity. It was ever thus.Reuse content