Understanding Scaling: Should I Pick Harder or Easier Subjects?
You have probably heard “pick the subjects that scale well”. Helpful intention, messy advice. In 5 minutes, here is the clearer version. No confusing language or maths; just a clear explanation and advice.
Scaling is a step used by UAC to calculate the ATAR. It is designed so you are not unfairly advantaged or disadvantaged by your particular mix of HSC courses. The key idea is that scaling reflects the academic strength of the students in a course, not how “hard” that course feels. It also does not change your rank within a subject.
So why do some subjects seem to scale up more often?
Courses with cohorts that, on average, perform strongly across all their subjects tend to end up with higher scaled means. UAC notes that Mathematics Extension 2 and Physics usually have high scaled means because they are studied by high achieving students.
Now let’s compare two extremes people talk about:
A “super hard” subject: Mathematics Extension 2:
Because the cohort is typically very strong academically, an HSC mark like 85 can contribute more, once scaled, than the same 85 in a mixed ability course. This is a cohort effect, not a reward for choosing difficulty. This means that, hypothetically, if heaps of academically strong students picked Mathematics Standard, it would also likely ‘scale up’.
A “super easy” subject: Mathematics Standard 1:
These courses are often seen as more accessible and attract a broader range of students. That wider spread can lower the scaled mean, so an 85 may contribute less than in Extension 2. That does not make the course a bad choice.
Here is the part students miss: your position matters as much as the course’s scaled mean. A higher rank in a lower scaling course can beat a lower rank in a high scaling course.
Practical advice we give families at North Shore Tutors
Choose the subjects you can score highest in, consistently. Scaling cannot rescue weak marks.
Protect your internal rank. NESA moderates school assessment marks using exam performance, so rank and exam preparation both matter.
Use scaling as a tiebreaker. If you are genuinely capable in a higher scaling course, go for it. If not, chasing it can backfire. For example, if you’re weighing up between chemistry or earth and environmental science, chemistry will likely score higher.
Scaling shifts each year because the strength of course candidatures shifts, so past conversions are only a guide.
If you are aiming for an extremely high ATAR and have shown consistently high academic performance throughout high school, only in this case do we recommend picking the highest scaling subjects.
High Scaling Subjects: All extension subjects, physics, chemistry, economics, biology.
In the end, the best “scaling strategy” is boring but reliable: pick courses that suit you, then maximise your rank and your raw marks.
