Cambridge IGCSE Grading Explained: The A*-G Scale and Core vs Extended

Cambridge IGCSE Grading Explained: The A*-G Scale and Core vs Extended

If your child is sitting Cambridge IGCSEs, the grading system will probably feel familiar at first glance — A* down to G, the same shape as the GCSEs many parents remember from their own school days. That familiarity is genuinely useful. But there's one part of the Cambridge system that catches a lot of parents off guard, and it has nothing to do with the letters themselves: in several subjects, the tier your child is entered for actually determines the highest grade they can achieve, regardless of how well they perform on the day.

Here's how the Cambridge scale actually works, what Core and Extended tiers mean in practice, and why raw marks don't map to grades quite as simply as they seem to.

The A*-G Scale Itself

Cambridge IGCSE grades run from A* at the top down to G, with U (ungraded) below that if a student doesn't reach the minimum standard. This is the scale Cambridge uses as its default across most international regions and at many UK independent schools that offer Cambridge IGCSEs — it's the traditional, longer-established grading system, in contrast to Edexcel's numerical 9-1 scale, which was introduced more recently specifically to add finer differentiation at the top end.

It's worth knowing that Cambridge does offer the 9-1 scale as an option in some regions, including parts of the UK, but schools are free to continue using A*-G if they prefer — and the majority do, in large part because international schools and universities told Cambridge they valued how well-understood and well-established the traditional scale already is. So if your child is sitting Cambridge IGCSEs, A*-G is almost certainly the scale you're working with, unless your specific school has explicitly opted into the numerical alternative.

For most universities and sixth forms, a C or above on the Cambridge scale is treated as an acceptable pass, with B and above generally expected for more competitive pathways, and A/A* reserved for genuinely strong performance relevant to scholarship applications or highly selective programmes.

Core and Extended Tiers: The Part That Actually Matters Most

This is the detail that trips up more parents than the grading scale itself. In several Cambridge IGCSE subjects — Mathematics is the most common example, but it applies elsewhere too — students are entered for one of two tiers, and the tier chosen determines the range of grades available before a single mark is even sat.

Core tier covers grades C through G. A student entered for Core, no matter how well they perform, cannot achieve an A or A* — those grades simply aren't available on that tier's grade range.

Extended tier covers grades A* through E. Extended papers include more demanding content and are pitched at a higher level throughout, which is the trade-off for access to the top grades.

This decision is typically made by the school, often based on a student's performance and teacher recommendation during the course, rather than being an open choice made independently by the student or parent. It's absolutely worth confirming directly with your child's teacher which tier they've been entered for, well before exams — not after results are already in hand — because it directly caps what's achievable and should shape how revision time and expectations are set throughout the year.

Edexcel has a broadly equivalent concept, called Foundation and Higher tier, on subjects like Maths and the sciences, so this isn't unique to Cambridge — but it's worth being aware of regardless of which board your child is on, since it's easy to overlook.

Why Raw Marks Don't Map Directly to a Grade

Much like Edexcel, Cambridge doesn't fix the number of marks needed for each grade in advance. Grade boundaries are set retrospectively, after each exam session, based on the overall difficulty of that particular paper and how the whole cohort performed — an approach generally described as "comparable outcomes." The aim is that a broadly similar proportion of students achieve each grade from one session to the next, regardless of whether a given year's paper happened to be harder or easier than usual.

In practice, this means a 90% raw score might result in an A* in one exam session and only an A in another, purely because the underlying paper's difficulty differed. It's a genuinely useful thing to understand when reviewing past paper practice: a strong raw percentage on an old paper is a reasonable indicator of ability, but it isn't a precise predictor of the grade your child would actually receive, since the live boundary for the paper they'll actually sit hasn't been set yet.

Cambridge publishes the specific grade boundaries for each subject and session after results are released, so if you want to see exactly how many marks were needed for a particular grade in a recent sitting, that's the authoritative source to check rather than relying on a rough percentage rule of thumb.

Does the Cambridge vs Edexcel Grading Difference Actually Matter?

For university admissions, no — not in any way that disadvantages one board over the other. UK universities, including Russell Group institutions, don't distinguish between Cambridge and Edexcel IGCSE grades when making admissions decisions; both scales are treated as equivalent, and a student presenting strong Cambridge A*-G results is read exactly the same way as one presenting strong Edexcel 9-1 results. What occasionally causes confusion is that individual universities or specific degree programmes sometimes state entry requirements in one scale without clarifying how it applies to the other — which is worth clarifying directly with the admissions office if your child's results are on a different scale than what's listed, rather than assuming a mismatch.

Getting the Right Support

Understanding the grading system is the easy part. Getting your child onto the right tier, and genuinely prepared for the demands of that tier, is where the real difference gets made — particularly for a subject like Maths, where a student capable of Extended-level work but entered for Core (or the reverse, a student struggling on Extended who'd be better served consolidating on Core) can end up with a result that doesn't reflect their actual ability.

If your child needs subject-specific support, Global Tutors matches students with tutors experienced in Cambridge IGCSE, including tier-specific preparation for Core and Extended — people who understand exactly how each tier is assessed and marked, not just the subject content in general.

A Few Quick Questions Parents Often Ask

Can my child move from Core to Extended (or the other way) partway through the course? It's possible in most schools, particularly earlier in the two-year course, but it becomes harder as exams approach since Extended content genuinely goes further than Core. It's worth raising with the school as soon as a mismatch is suspected, rather than waiting.

Is Extended tier always the "better" choice? Not necessarily — Extended access to top grades comes with more demanding content throughout, and a student who'd struggle to keep pace may get a stronger, more confidence-building result on Core than a weaker one straining through Extended. The right tier depends on the individual student, not a blanket preference for the higher-ceiling option.

Why did my child's grade seem lower than their raw percentage suggested? Grade boundaries are set after the exam based on that specific paper's difficulty and how the whole cohort performed, so raw percentage alone doesn't translate directly into a grade — the boundary for that exact session determines it.

Does Cambridge ever use the 9-1 scale instead of A*-G? Occasionally, in some regions including parts of the UK, but the large majority of Cambridge IGCSE students worldwide are still graded on the traditional A*-G scale, since most schools have chosen to stick with it.

Global Tutors provides subject-specific tutoring for IB, Cambridge, IGCSE, and IEB students, matched with tutors who know your child's exact exam board, syllabus, and marking standard. Get in touch for a free consultation.