A Simple Guide to HSC and ATAR Scaling

📝 The HSC

The HSC (Higher School Certificate) is the final part of education in NSW.

The purpose of the HSC and the ATAR is to ensure school leavers are ready to enter the workforce and/or tertiary education.

Units

The HSC is built on units. To get your certificate, you need to complete 12 units in Year 11, 10 units in Year 12 (to get an ATAR).

• Most subjects (like English Advanced, Biology) are 2 units.
• Extension subjects (like Maths Extension 1, English Extension 1) are 1 unit.
• Some courses, such as Mathematics Extension 2, are worth 4 units when combined with Mathematics Extension 1.

Most students take 11 to 12 units to give themselves a buffer. In recent years, students have been taking exactly 10 units, leaving them with little room to breathe.

Internal Assessment

Your final HSC mark in each subject is a 50/50 split:

• 50% from your internal school assessments (the tests and assignments you do all year).
• 50% from your final HSC exam.

The internal assessment mark is composed of Year 12 tasks (note that Year 12 begins in Term 4 of Year 11). Generally, it consists of an exam, some assignments, a practical (for science students), and a Trial HSC exam.

The HSC Exam is a standardised exam that all students sit and is used in moderation (more on this soon).

The two marks then come together (after scaling and moderation) to produce your final HSC mark, which is the average of the Internal Assessment and Exam mark.

📈 HSC Scaling (Moderation)

HSC Moderation allows you to compare schools

The question then arises, how can one mark from one school be fairly compared to another school?

How can NESA (NSW Education Standards Authority) be sure that a mark of 90% at one school represents the same level of achievement as a 90% at another? The internal assessments (exams and assignments) are different.

This is where moderation comes in. Moderation is the process used to make marks from different schools comparable; it is often referred to as HSC Scaling.

Think of it like this: Imagine two runners 🏃 are trying to qualify for a race. One runs on a flat, easy track, while the other runs on a steep, challenging track. It wouldn't be fair to compare their raw times directly. You need a way to adjust their times to account for the difficulty of their track.

In the HSC, the HSC exam is the "standard track" that everyone runs on. NESA uses the performance of your school's students in the final exam to adjust your school's internal assessment marks.

Let's examine two students from two schools, Alice and Bob, who have the same internal assessment mark (80) and perform the same in their HSC Exam (80).

Alice's school set slightly easier assessments overall, as indicated by the lower average HSC Exam mark (76). Bob's school assessments were more complex, as shown by the overall average in their HSC exams (80)

Alice's HSC Moderation

Alice's school had easier exams overall, so her internal assessment mark has been moderated down.

Bob's HSC Moderation

Bob's school had harder exams overall, so his internal assessment mark has been moderated up.

Importantly for any student:

• It doesn't change your rank within your school group. If you came 1st in your class for internal assessments, you will still be 1st after moderation, so the rank in your school assessments does matter. Your hard work in school assessments is a crucial part of the HSC process.
• It does adjust the marks up or down to align with how your group performed in the exam. So your school matters when it comes to the HSC.

While often confused with scaling, it's actually HSC moderation that allows for a fair comparison of students from different schools. It ensures that your hard work is valued equally, regardless of where you attended school. Your efforts in the HSC and ATAR process are not in vain; they are recognised and rewarded.

🏅 The ATAR

The ATAR (Australian Tertiary Admission Rank) is not a mark; instead, it's a rank. It allows universities to compare students regardless of the subjects they took or where they took them. An ATAR of 85.00 means you performed better than 85% of your peers. It’s the leading tool universities use to select students.

Every unit is taken out of 50, so if you scored 86 in a 2-unit course, then your mark for each unit is 43.

So, how is that magic number calculated? UAC (the Universities Admissions Centre) uses a simple recipe based on your best 10 units.

1. Your best 2 units of English are always included. It’s the compulsory foundation of your ATAR.
2. Next, UAC selects your top 8 units from your remaining subjects.
3. These 10 scaled units are added together to get your aggregate score out of 500.
4. Your aggregate is then ranked against everyone else's to determine your ATAR.

If you study more than 10 units, the extra ones act as a safety net. UAC only picks your best, so you’re never penalised for taking on more. This means that if you perform better in the additional units, they will be included in your ATAR calculation, potentially boosting your overall score.

The key missing point is HOW the scaled marks are calculated? The answer is ATAR scaling. Let's look at how this works.

🎓 ATAR Scaling

ATAR Scaling allows you to compare subjects

Just as it's hard to compare assessments between schools, it's also hard to compare performance between different subjects. Is a mark of 85 in Advanced Mathematics the same achievement as an 85 in Visual Arts? The courses are entirely different.

This is the problem that scaling solves. The goal of scaling is to allow the Universities Admissions Centre (UAC) to compare student achievement across all subjects fairly. It works by evaluating the overall academic strength of students who take each subject.

If a subject (like Physics, for example) is taken by students who perform very strongly across all their other subjects, the candidates for that subject are considered very strong.

Scaling adjusts your raw HSC marks based on the strength of this competition. A high mark in a subject with a strong candidature will be scaled higher than the same mark in a subject with a weaker overall candidature.

ATAR scaling allows for a fair comparison of performance across different subjects. It attempts to estimate what you would have achieved if every student had taken every subject.

Example of Scaling

The graph illustrates how scaling maps an HSC mark to a scaled mark used in ATAR. You can see that specific subjects scale better. For instance, the high scaling moves your marks up (e.g. HSC Maths Ext 2), medium scaling is still good (e.g. HSC Maths Adv), and low scaling scales down (e.g. HSC Society and Culture)

This process produces your 'scaled marks', which are added together to create an aggregate. This aggregate is then used to determine your final ATAR rank.

Crucial takeaway: You should not choose subjects just because you think they "scale well". The best way to achieve a good ATAR is to choose subjects that you excel in and genuinely enjoy.

A high raw mark in a "lower scaling" subject will almost always result in a better outcome than a poor mark in a "higher scaling" subject.

💻 Example Calculations

Disclaimer: These examples use hypothetical marks and illustrative scaled marks. The actual scaling changes every year. The HSC Mark is what you see on your NESA certificate, while the Scaled Mark is the value UAC uses to calculate your aggregate.

A scaled mark is calculated out of 50 for each unit (so a 2-unit subject has a total scaled mark out of 100).

Also it's important to note that we use raw HSC marks as the input (not the mark that you see in your HSC).

Example 1: Alex the All-Rounder

Alex is a strong, consistent student who studies 12 units across a broad range of subjects.

Aggregate Calculation:

The ATAR is built from the best 10 units, and the 2 units of English must be included.

1. Start with English: Alex's 2 units of English Advanced are compulsory.

2. Aggregate so far: 82

3. Add the next best 8 units: UAC now takes the next best 8 units based on the scaled marks.

4. Add Business Studies (2 units): 82 + 88 = 170

5. Add PDHPE (2 units): 170 + 84 = 254

6. Add Visual Arts (2 units): 254 + 78 = 332

7. Add Mathematics Standard (2 units): 332 + 74 = 406

8. Identify dropped units: Alex's 10 units are now filled. The subject with the lowest scaled mark, Studies of Religion I, is dropped from the calculation.

Final Result:

• Aggregate: 406 / 500
• This aggregate would likely result in an ATAR in the low 90s.

Example 2: Ben the STEM Star

Ben loves a challenge and studies 10 units focused on high-level Maths and Science. This example illustrates how strong performance in subjects with highly achieving student groups (candidature) can impact scaling.

Note: In Ben's case, his HSC mark of 95 in Maths Extension 2 resulted in a scaled mark of 96. This is a rare effect that can happen in subjects with exceptionally strong candidatures, where the overall academic strength of the students is so high that the scaling process adjusts top marks upwards.

Aggregate Calculation:

Because Ben only studied 10 units, all his subjects will be included in the calculation.

1. Start with English: Ben's 2 units of English Advanced are compulsory.

2. Aggregate so far: 84

3. Add the next best 8 units:

4. Add Maths Ext 2 (2 units): 84 + 96 = 180

5. Add Maths Ext 1 (2 units): 180 + 92 = 272

6. Add Chemistry (2 units): 272 + 90 = 362

7. Add Physics (2 units): 362 + 88 = 450

Final Result:

• Aggregate: 450 / 500
• This very high aggregate would translate to an ATAR in the 99+ range.

🤔 Need more help

Get in touch

At Intuition, we're always happy to explain these in person. Our teaching and learning team can provide detailed explanations of the HSC and ATAR.

If you'd like to visit us to gain a better understanding of the HSC and ATAR, please contact us

ATAR Calculators

We often get asked about ATAR calculators. They can give you a rough estimate based on subjects, but it's not a healthy way to look at your marks. Spending hours on an online ATAR calculator is one of the worst things you can do. Here’s why:

1. They Are Not Always Accurate. Calculators use scaling data from previous years. This data changes every single year. The calculator is making a guess based on old information—it cannot predict the future.
2. They're a Procrastination Tool. It feels productive, but it's not. The time you spend plugging in imaginary marks could be spent doing practice papers or writing an essay—things that actually improve your marks.

Don't let them cause you stress or give you a false sense of security. Focus on what you can control.

Some useful sites:

• NSW Education Standards Authority (NESA). (2023). HSC Moderation
• Universities Admissions Centre (UAC). (2024). What is the ATAR?
• Universities Admissions Centre (UAC). (2024). The Scaling Process