Choosing A Level subjects is the first academic decision where the wrong answer costs you options rather than marks. It’s also usually made in a fortnight, in the middle of exam season, on the basis of which teachers you liked.

There is a better way to do it, and it starts with reading four pages.

Start with the syllabus, not the subject name

Subject names are misleading. What the course actually is sits in the syllabus, on the Cambridge website, free.

Two sections matter. Previous study tells you what the course assumes you arrive with. The assessment objective weightings tell you what the examiner pays for.

Look at what that reveals:

• Economics 9708 recommends a course in mathematics equivalent to IGCSE Extended or O Level. It does not recommend prior Economics. Students often pick it to avoid maths and find the maths assumption waiting.
• Literature in English 9695 recommends a level of English equivalent to first language English at IGCSE. If you took English as a Second Language, you are starting below the level the course is written for.
• Mathematics 9709 assumes IGCSE 0580 Extended or O Level 4024/4029, plus simple manipulation of surds and the shapes of graphs of the form y = kxⁿ.

Ten minutes per subject. It is the highest-value reading you will do all year.

How many: three, or three and a half

Three A Levels is the standard load. University offers are built around three, and the fourth rarely changes an offer.

Run the hours before adding one. Cambridge designs each A Level around about 360 guided learning hours against roughly 130 for an IGCSE. Across a school year of about 36 teaching weeks over two years, that’s around five hours a week per subject of taught time, with independent work on top.

• Three subjects: about fifteen hours a week of guided learning.
• Four subjects: about twenty.

That fourth subject is not a bit more work. It’s a third more, permanently, for two years, and the time comes out of the three that your offer depends on.

Take a fourth if you have genuine surplus capacity and a reason: Further Mathematics alongside Mathematics, or a subject a specific course requires. Don’t take one as insurance against a subject going badly, because the insurance costs more than the risk.

The combination question

Some combinations open doors. Others quietly close them, and you don’t find out until you’re writing applications.

Mathematics is the most enabling single choice. It is required or strongly preferred for engineering, physics, computer science, economics and most quantitative degrees. If you’re undecided and capable at it, it keeps the widest range of routes available.

Sciences work in pairs. Medicine and biomedical routes typically want Chemistry plus Biology. Engineering wants Maths plus Physics. A single science on its own is rarely the requirement.

Breadth is not free. Three unrelated subjects can look well-rounded and satisfy no specific course requirement. If you know the destination, work backwards from it.

The reliable method is dull and takes an evening: pick three universities and two courses you might want, find their entry requirements, and write down what they actually ask for. Requirements vary by country and by course, and general lists go out of date.

Do this even if you’re undecided about a career, and especially then. You’re not committing to a destination; you’re finding out which subjects are load-bearing for several destinations at once. A subject that appears in four different requirement lists is doing more work than one that appears in none, and that’s knowable now.

Two failure modes to watch for. The first is choosing three subjects that all serve the same narrow route, which is efficient if you’re certain and costly if you aren’t. The second is choosing three that serve no route in particular, which feels safe and quietly rules out anything with a specific prerequisite.

The middle position is usually right: two subjects that keep your likeliest routes open, and one you chose because you want to study it.

Enjoyment is a practical criterion, not a soft one

This gets dismissed as the sentimental factor. It’s the opposite.

You are committing about 360 guided learning hours per subject, plus independent study, across two years, and the independent half is unsupervised. Nobody will chase you through it.

A subject you find genuinely interesting gets those hours. A subject you chose strategically and dislike gets the minimum you can get away with, and at A Level the minimum is visible in the grade. Interest is the mechanism that makes the workload survivable, which makes it a strategic consideration rather than a nice-to-have.

The qualifier: interest in the subject as it’s actually assessed, not as it sounds. Which brings us to the most common mistake.

Check how the subject is marked, not how it sounds

Subjects are hard in different ways, and the difference is published.

Subject	Knowledge and understanding at A Level	The rest of the marks
Biology 9700	40%	Handling and evaluating information 40%, experimental skills 20%
Economics 9708	35%	Analysis 40%, evaluation 25%
Literature in English 9695	20%	Analysis, personal response, communication and evaluation, 20% each

If you retain content well but write slowly, Biology’s 40% knowledge weighting suits you. If you argue well and forget detail, Literature’s spread suits you better.

Two specifics worth knowing before you commit:

The sciences examine practical work heavily. Biology 9700 puts 20% of the qualification on experimental skills, across Paper 3 (Advanced Practical Skills, 2 hours) and Paper 5 (Planning, Analysis and Evaluation, 1 hour 15). The syllabus states that the context of questions in those papers may be outside the syllabus content, so you can be examined on an experiment you’ve never seen.

Literature adds a skill in Year 13. AO5, evaluation of opinion, is worth 0% at AS Level and 20% at A Level. A fifth of the final grade rests on something that wasn’t assessed in your first year.

Maths splits into three, so pick with your eyes open

If you’re taking Mathematics 9709, know what you’re signing up for.

It isn’t one subject. Pure Mathematics, Mechanics, and Probability & Statistics are separate strands. For the full A Level, Paper 1 (Pure Mathematics 1) and Paper 3 (Pure Mathematics 3) carry 30% each and Paper 5 (Probability & Statistics 1) carries 20%. The last 20% is either Paper 4, Mechanics, or Paper 6, Probability & Statistics 2, and your school usually decides which.

If your school runs the Mechanics route, a fifth of your maths grade is forces and motion. That’s worth knowing if you dropped Physics.

One trap sits in the same syllabus. Paper 2, Pure Mathematics 2, is offered only as part of an AS Level and isn’t available for the A Level, so an AS built from Papers 1 and 2 doesn’t carry forward into the full qualification.

The AS Level question

Cambridge designs an AS Level around about 180 guided learning hours, half a full A Level, and it exists as a qualification in its own right.

Some schools enter students for AS components at the end of Year 12 and complete the A Level in Year 13. That turns one enormous end point into two, gives you a grade in hand, and suits students who prefer checkpoints.

Others teach linearly to the end of Year 13. Whether the staged route is available depends on your subject and your school’s policy, and it’s a question worth asking before you choose subjects rather than after.

What if you change your mind

Most students who worry about this are worrying about the wrong risk.

Changing a subject in the first few weeks of Year 12 is usually possible and usually fine. Schools expect some movement early, and the material covered by then is small enough to catch up. If a subject is clearly wrong in September, say so in September.

Changing in Year 13 is a different proposition. By then a year of a 360-hour course sits behind the class, and starting fresh means covering it alongside everything else. That’s the change worth avoiding, and it’s avoided by taking the first few weeks seriously as information rather than as a settling-in period.

The genuine risk is subtler. It’s picking a subject a course requires, disliking it, and doing the minimum for two years. That produces a grade too low for the course the subject was chosen to enable, which is the worst of both outcomes. If you can see that coming in October, it is better to change the subject or change the destination than to spend two years splitting the difference.

Don’t choose on last year’s teacher

A subject and the person who taught it to you are different things, and at A Level they come apart.

The teacher will probably change. The content certainly does. IGCSE Biology and A Level Biology share a name and a fifth of the assessment approach: 9700 puts 20% of the qualification on experimental skills across two practical papers, which is not what IGCSE practical work felt like.

The same applies in reverse. A subject you disliked at IGCSE may be a different experience when it stops covering everything shallowly and starts going somewhere. Maths is the common case, because A Level maths spends far more time on why a method works and less on drilling arithmetic.

The reliable signal is the syllabus content list, not last year’s classroom. Read what the two years actually cover before deciding you know what the subject is.

A method you can finish this week

1. List five or six candidate subjects. Include anything you’re good at and anything a possible course requires.
2. Open each syllabus. Read Previous study and the assessment objective weightings. Ten minutes each.
3. Check two real courses. Find the entry requirements at two universities you might apply to and write down exactly what they ask for.
4. Cut to three. Keep anything a course requires, then anything you’ll actually spend unsupervised hours on.
5. Audit the assumed skills. For each surviving subject, mark each assumed skill as automatic, slow, or gone.
6. Ask your school about the AS route and, for maths, which fourth paper they enter.

Step five is the one that changes your first term. Everything on the slow or gone list is what August is for, because none of it gets retaught.

What to do with the list

If a subject you want assumes something you don’t have, that’s a gap to close rather than a reason to drop the subject. Assumed skills are usually a short list, and the summer between exams and Year 12 is long enough to close most of it.

For what that summer looks like in practice, see the gap between IGCSE and A Levels. If you want to know which of your choices carries the biggest step up, which A Level subjects have the biggest jump works through them with the syllabus numbers. And if you’re weighing whether the jump needs paid help, who needs an A Level bridging course includes the case for doing it yourself.

If maths made your final three, it is worth arriving with the assumed skills automatic, because they sit underneath Physics, Chemistry and Economics as well. Pre-A Level Mathematics maps the route from 0580, 0607, 0606 and O Level 4024 into 9709.

Frequently asked questions

How many A Levels should I take? +

Three is standard and is what universities build offers around. A fourth is worth considering only if it is genuinely surplus capacity rather than borrowed time, because each subject is designed around about 360 guided learning hours. A fourth subject adds roughly five hours a week of taught time across two years.

Which A Level subjects keep the most degree options open? +

Mathematics is the single most enabling choice, because it is either required or strongly preferred for engineering, physics, economics, computer science and many quantitative degrees. Beyond that, check the entry requirements of two or three specific universities rather than relying on general lists, since requirements vary by country and course.

Can I take an A Level subject I have never studied before? +

Often yes, but read the syllabus first. Cambridge Economics 9708 recommends prior study of mathematics equivalent to IGCSE Extended or O Level, and no prior Economics. Literature in English 9695 recommends a level of English equivalent to first language English at IGCSE, which is a real barrier for some students.

Does my IGCSE grade decide whether I can take a subject? +

Schools set their own entry grades, but Cambridge states prior study as having completed a course rather than achieved a grade. Mathematics 9709 assumes IGCSE 0580 Extended or O Level 4024/4029. What matters more than the grade is whether the assumed skills are fluent, because none of them are retaught.

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