Plenty of students finish IGCSEs without a settled final three. School options may not be confirmed, results might change something, or the choice is genuinely still open.

The usual advice is to wait. That is unnecessary, because most of what A Level assumes is the same regardless of which subjects you end up taking.

The assumed lists overlap more than the subjects do

Read several Cambridge prior-knowledge statements side by side and a pattern appears quickly.

Mathematics 9709 assumes IGCSE Mathematics 0580 Extended or O Level 4024/4029, plus simple manipulation of surds and the shapes of graphs of the form y = kxⁿ.

Physics 9702 recommends Physics or Co-ordinated Science to IGCSE standard, then separately prints a mathematical requirements list covering arithmetic, standard form and graphs, and states that teaching it should be included in the Physics course.

Chemistry 9701 carries its own mathematical requirements section alongside its subject entry.

Economics 9708 does not assume Economics at all. It recommends a course in mathematics equivalent to IGCSE Extended or O Level.

Four different subjects, and the same skill keeps appearing underneath them. That is the answer to the timing problem: the shared foundation is knowable before the choice is.

The three things worth doing while undecided

None of them commits you to anything.

Algebraic fluency. Rearranging formulae, index laws, standard form, surds, reading a gradient. This is the single most transferable item on any assumed list, and it is examined inside other subjects rather than only in maths. Weak algebra in Physics 9702 does not present as a maths problem; it presents as a physics mark.

Reading data. Graphs, tables, percentages, index numbers. Economics 9708 puts 40% of the qualification on analysis and 25% on evaluation, and both are performed on data you are handed. Biology 9700, Chemistry 9701 and Physics 9702 each put 40% on handling, applying and evaluating information.

Writing a sustained argument. Four hundred words that argue rather than describe: a claim, the mechanism, the strongest objection, why the claim survives. That is the shape of the marks in Economics, Business and Literature, and it is the skill that moves most between IGCSE and A Level in all three.

Do those and you have prepared for essentially any combination.

What not to do while undecided

One thing, and it is the obvious temptation.

Do not pre-learn Year 12 content for a subject you might not take. That is the only genuinely wasted version of this work, and it is wasted twice over: your class would teach it again anyway, at the pace the exam requires, and if you drop the subject it evaporates entirely.

The distinction is between the syllabus and what sits underneath it. Content is subject-specific and gets taught. Assumed skills are shared and never get retaught.

Using the uncertainty productively

Being undecided has one advantage worth using before it closes.

You can read the syllabuses of the subjects you are weighing, which is the most useful ten minutes available and almost nobody does it. Read two sections: Previous study, and the assessment objective weightings.

That tells you things the subject name does not. Business 9609 weights all four objectives equally at 25% each at A Level, having been 40% knowledge at IGCSE — so it rewards judgement far more than recall. Literature in English 9695 runs five objectives at 20% each, and only one is knowing the texts. Computer Science 9618 puts 40% of the A Level on designing, programming and evaluating.

If you are choosing partly on what you are good at, those weightings are better evidence than the subject’s reputation.

The decision has a deadline you may not have noticed

Worth saying plainly, because undecided students often assume more time than they have.

Schools build timetables over the summer, and subject blocks constrain which combinations are possible. Waiting for August results before saying anything can mean discovering in the last fortnight that your preferred pair does not fit.

If you are genuinely open, tell your school now rather than in September, and ask which combinations are actually available. That conversation frequently narrows the choice more than the deliberating does.

The subjects that change the calculation

Two situations narrow the advice, and both are worth checking before settling into general preparation.

If Mathematics is even possible, prepare for it. It is the most enabling single choice for quantitative degrees, it has the longest assumed list of the common subjects, and its foundation shows up inside Physics, Chemistry and Economics regardless. Preparing for maths is close to a free option: if you take it, you needed it, and if you do not, the algebra still appears in whatever you chose.

If a science is possible, look at the practical component now. Biology 9700, Chemistry 9701 and Physics 9702 each put 20% of the qualification on experimental skills, examined in two papers whose contexts may fall outside the syllabus content. That is a fifth of the grade resting on a skill nobody practises in advance, and knowing it exists changes how you approach Year 12 practicals from the first week.

Neither requires the decision to be made. Both mean that if the subject is on your shortlist, some of the preparation is worth doing before the shortlist closes.

What to do in what order

A workable sequence for a student who does not yet know.

1. Weeks one to three: rest. Non-negotiable, and it is not contingent on the decision.
2. Week four: read four syllabuses — the subjects you are weighing. Previous study and assessment objectives only. About forty minutes total.
3. Weeks four to eight: work the shared skills. Algebra, data reading, one written argument a week. Three or four sessions a week of forty minutes.
4. When the choice settles: read the prior-knowledge page for the three you land on, and spend the last stretch on anything subject-specific that appears.

The first three steps are identical whichever way you decide, which is the whole point.

If the uncertainty is between very different subjects

The advice above assumes your options overlap. Sometimes they do not — a student weighing Physics against Literature has two genuinely different assumed lists.

Even then, one thing still transfers. Both subjects will ask you to sustain an argument or a method across a longer piece of work than IGCSE required, and both mark how you got there rather than only where you arrived.

Beyond that, use the uncertainty as a test rather than a problem. Spend one session on algebraic fluency and one on writing a four-hundred-word argument. Notice which felt like effort and which felt like interest.

That is genuinely useful information for the decision itself, and it is better evidence than imagining what a subject will be like. A student who finds the writing session absorbing and the algebra session tedious has learned something about their next two years that no prospectus will tell them.

And if the answer is that neither felt bad, you have prepared for both, which was the point.

Where to start

The shared foundation is mostly numerical, which makes it the easiest part to work on without a decision. Pre-A Level Mathematics opens with Algebraic Fluency and covers Functions and Graphs and Statistics Foundations, all of which sit underneath the sciences and Economics as well as maths itself.

If maths is definitely on your list, that is the obvious place to spend the summer. If it is not, the same algebra still turns up inside whatever you do choose.

For the choice itself, how to choose A Level subjects covers selection and how many to take, and which A Level subjects have the biggest jump compares them using the syllabus numbers.

Frequently asked questions

Can I prepare for A Levels before choosing my subjects? +

Yes. The assumed skills overlap heavily across subjects, and numeracy in particular sits underneath most of them. Cambridge Economics 9708 assumes a mathematics course rather than an Economics one, and Physics 9702 prints a mathematical requirements list it expects taught inside the course.

What preparation is useful whatever subjects I take? +

Algebraic fluency, reading data from graphs and tables, and writing a sustained argument to a length. Between them those three cover the assumed skills of the sciences, Economics, Business and the essay subjects, so none of the work is wasted whichever three you settle on.

When do I actually have to decide? +

Usually before or just after your IGCSE exams, since schools build timetables over the summer. If you are genuinely undecided, that is worth raising with your school early rather than assuming the decision can wait until results arrive in August.

Is it a waste of time preparing for a subject I might drop? +

Not if you prepare the shared skills rather than subject content. Pre-learning Year 12 Chemistry would be wasted if you drop Chemistry. Getting rearranging and standard form automatic is not, because those appear in Physics, Chemistry, Economics and Maths alike.

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