The IB, or International Baccalaureate, was founded in 1968 in Geneva, Switzerland (at my high school in fact!). Since then, it has grown into a prestigious program with over 140000 candidates in its Diploma Program (DP) each year. The DP has a reputation for being extremely academically challenging, to the extent that IB graduates often start university with multiple course credits already under their belt.
I completed my diploma in 2020, having taken Further Math, Physics & Chemistry as my higher level subjects. When I started by undergraduate program at Brown University, I was able to skip 3 math classes and 2 chemistry classes, which would otherwise have taken a year to complete.
This article is focused on IBDP Mathematics, in which there are actually 4 separate courses. My goal is to help you get to know IB Math through numbers. We'll answer questions like
How many people take IB Math each year?
What is the global distribution of IB Math students?
What are the historical grade boundaries in the different versions of IB math?
and more...
The growth of IB Math through the years
The IB refers to its students as candidates (by the time you take your exams you will know yours by heart). The IB organizes two exam sessions per year. The first session is around May, and the second around November. Most candidates taking exams in November are students in the southern hemisphere, where summer break starts in December. Because there are simply more people in the northern hemisphere, there are far fewer candidates in November than May.
The bar chart above shows the evolution of IB Math cohort sizes since 2014. The latest exam session, May 2025, counted 118'713 students, compared to 80'094 in 2014. Let's do a bit of math:
or a roughly 48% increase over 2025−2014=11 years. Per year, this represents a growth of
But look at the chart! COVID clearly halted the IB's growth for 3 whole years. Let's correct for that:
To put that in perspective, if the same rate of growth were to continue, the number of candidates in the May session would reach 200'000 in
which is in 2036!
A similar analysis shows that the November session is growing much faster - at a rate of 9.4% per year.
The Breakdown of AA vs AI and SL vs HL
The IB offers 4 different versions of its Math syllabus. The Analysis & Approaches (AA) program emphasizes reasoning and analysis, while the Applications & Interpretations (AI) is more focused on - you guessed it - applications. Both programs are offered as standard or higher level (SL or HL) subjects. Stay tuned for an article helping you decide which is best for you.
Although AA and AI are designed to be equally (but not equivalently) challenging, most students (and many teachers) believe that AA is harder than AI, particularly at the standard level. This is a self-reinforcing belief, as students who see themselves as mathematically proficient gravitate towards the "harder" program. That makes it harder to determine statistically which courses, if any, are harder or easier.
The diagram above breaks down the number of students in each of the 4 math programs (averaged over 2021-25), with a pie chart for each session. There are a lot of interesting things to note here:
AAHL has the highest average (5.07 in May) and highest fraction of 6's and 7's.
AISL has the lowest average (4.16 in May), with over a third of AISL students failing altogether.
Students score significantly worse in November, except in AAHL where they score somewhat higher.
Relatively few students take AIHL.
The longer you stare at the chart, the more insights you'll discover. But I've given you the most important ones.
Please note that a higher average does not mean a subject is easier. AAHL has a higher average than AASL, but it is by definition more challenging.
Grade Boundaries
I remember being shocked the first time I saw the grade boundaries for IB Math. For in class tests, teachers often used 90% or 92% as the benchmark for a 7. On the IB, that number is usually in the mid to high 70s!
The diagram above summarizes the historical grade boundaries in each of the 4 IB Math courses. If you'd prefer to read a table:
Here are the key things to notice:
A score in the low 80s will almost guarantee you a 7.
The grade boundaries vary from year to year, especially in SL.
Statistical Grading
The reason for all this change is that the IB employs a statistical grading technique. At a high level, for each session:
Start by assuming the current students have identical ability to the year prior, and set provisional grade boundaries to match the proportion of 7s and passes from the previous year.
Check whether the new cohort seems stronger or weaker than the previous year, and adjust accordingly. This is done in a few ways:
Compare the outcomes at schools with a similar number of candidates as in the previous year. If most schools are performing better only in Math, that probably means the exams were easier, and boundaries are adjusted accordingly.
Analyze student performance across subjects - there is usually some correlation.
Examiners analyze results question by question to detect any unfairly hard problems, and look at full examples of students near grade boundaries to inform the final adjustment.
May vs November grade boundaries
A somewhat controversial IB fact is that in AAHL, the November grade boundaries are significantly higher than those in May:
However, if you return to the pie charts shown earlier, you will see that November AAHL students perform better than May AAHL students, even with higher grade boundaries!
What's going on? Either
AAHL Exam papers tend to be easier in November (this seems somewhat true to me)
AAHL students in the southern hemisphere are stronger.
It is worth noting the average Diploma score (out of 45) in November 2024 was 30.3, a full point higher than May 2023's 29.3 average. The two sessions have different geographic distributions, and a higher proportion of November session schools are private (76.7% vs 59% in 2024).