We’re picking straight back up from where we left off in Part 1. You’ve met our 5 model students - Jasper, Rachel, Scott, Amelia, and Mohammed—each attending Number One School with their own academic strengths, interests, and career aspirations. Now, it’s time to tackle one of the biggest questions on every HSC student’s mind: How does the ATAR actually work?
In this part, we’ll break down how your HSC marks are calculated, how your school’s performance affects your results, and what goes into determining the final ATAR ranking. Whether you’re aiming for a top percentile score or just want to understand the system, we’ve got you covered. Let’s get into it!
Let’s start off with an easy topic. The concept of “bands” in the HSC is different to that of NAPLAN and other assessments. HSC bands are simply a way to categorise or “round” students’ marks to the nearest 10 - and hence achieving a particular band is only a rough indication of achievement in that course.
For standard HSC courses, student performance is divided into six bands:
For extension courses, which are more advanced and typically taken by high-achieving students, the performance bands are different:
So now you know all about bands and achievement, let’s fast-forward a year and a bit, to a particularly poignant time - HSC results day! All five of our students have put in effort over the past 12 months to get their HSC scores (and ATARs). But before we start looking at tables and numbers, let’s see where these marks came from.
Part 1: School scores
To make the HSC fairer and less stressful, 50% of the total score comes from school assessment tasks that our students have submitted throughout the year. These assessments help balance out the pressure of final exams and reward consistent effort rather than just a single test performance. Examples of school assessments at Number One School include Jasper’s hand-in English Extension 1 essay (marked by his teacher), Rachel’s in-class Maths Extension 2 test (written and marked by her teachers), Scott’s Legal Studies multimedia presentation (set and marked by his teacher), Amelia’s dramatic monologue (guided and assessed by her teacher), and Mohammed’s Arabic listening and speaking test.
But it’s not as simple as taking the average of all the marks students get in school and making that half of the final HSC mark - because some teachers (and some schools) set tougher assessments and/or have higher standards than others! Here’s where scaling comes in - but we’ll skip over this for now. For now, just assume that everyone’s mark has been put through a magic computer that makes all school scores fair and true!
Part 2: External exam scores
External exam scores are much simpler and more intuitive - a student gets a particular (aligned) mark in their standardised government exams for that subject at the end of the year, and this counts to 50% of their total score in that subject (as well as helping to scale the school scores, but we’ll worry about that later). Every student studying a subject sits the same government exam(s) and is marked exactly the same way, so it’s a lot easier to be consistent here. Some subjects have more than one external exam (e.g., English Advanced, which has the Human Experiences (Common Module) Paper 1 and the Modules (A, B, and C) Paper 2), while others have only one (e.g., Biology, which has just one 3-hour paper examining all of the modules equally).
Part 3: Final marks!
Now, we simply take the average of the moderated school and aligned external exam marks and round up (never down) to get the student’s final HSC mark, delivered to them on results day in a table that looks like this:
| Course name | Units | Examination mark (exam score) | Assessment mark (school score) | HSC mark (average of previous two) | Performance band |
|---|---|---|---|---|---|
| Biology | 2 | 96 | 95 | 96 | 6 |
| English Advanced | 2 | 96 | 98 | 97 | 6 |
| English Extension 1 | 1 | 48 | 48 | 48 | E4 |
But, you might ask, how do we actually get the moderated and aligned marks from the student’s actual raw marks (i.e., how many points they collected/lost during an exam) in their school and external assessments? Let’s take a look!
Parents, students, and even tutors have definitely heard (and maybe talked) about the term scaling. For many, it is merely a mysterious concept that somehow makes attending a highly-ranked school and picking particular maths/science subjects the most important part of completing the HSC! Well, we’re here to clear the air around this complex and multifaceted mechanism that ultimately makes the HSC fairer for all by calculating those aforementioned final marks. Let’s dive in.
Firstly, it’s important to note that there’s not just “one type” of scaling, but three - marks are scaled at an individual, school, and subject level.
Of the 3 types of scaling, this is the easiest to understand. Alignment is performed by NESA. It converts raw marks in external exams to final marks that correspond with bands to indicate the individual student’s level of performance against the different bands in a subject.
Remember that bands are indicators of performance - but sometimes raw (actual) marks don’t always match to bands directly! For example, Rachel did both Business Studies and Maths Extension 2, of which we can assume that Maths Extension 2 is a much harder subject.
So, if Rachel lost 35 actual marks in her Maths Extension 2 exam (e.g., by making 35 careless mistakes), she would get a raw exam mark of 100-35 = 65. But she shouldn’t necessarily get a final score of 65 - this is because if Rachel got a 65 for her final Maths Extension 2 mark, she would fall into the “satisfactory” Band 3 category, with only a “solid understanding of the course requirements”. But, in actual fact, a raw mark of 65 indicates a very high level of achievement according to the syllabus, as NESA decided it’s very easy to lose 35 marks in 4U maths, even if you’re a really smart student - so Rachel’s 4U maths raw mark of 65 might be aligned to a final mark of 90 which represents outstanding achievement (Band 6) according to the bands.
On the other hand, if Rachel also lost 35 raw marks in Business Studies, her external exam score might actually be lower, to account for the reduced difficulty; this is because losing 35 marks in Business Studies means she only has a sound understanding of the course content, not a basic understanding. So, her Business raw mark of 65 might be aligned to a final mark of 75 which represents sound achievement more accurately.
This alignment formula is the same for every student (so that a final mark corresponds directly to a skill level in each subject), and it is only carried out on external exam marks - internal (school) marks don’t depend on it, because of…
Moderation is the most complicated type of scaling. It involves making school marks fair for everyone. This is because the standards of (and marks given by) each school, i.e., the difficulty of their internal exams and assessments and the corresponding performance of their cohort, differ greatly. So, the standards of each school are measured through how well their cohort performs in external exams, which are of consistent difficulty each year and taken by students across the entire state. The external exam serves as the guide for comparing students from different schools directly to each other through the use of a moderated school mark.
Let’s look at some examples. If, on average, students in Number One School who score 70% in their internal exams then achieve 90% in their external exams, then a 70% raw school mark from Number One School will be treated as (i.e., “scaled to”) a true school mark of 90%. This adjustment is made to reflect the higher level of difficulty of Number One School’s internal assessments - as the same students with the same level of skill got 70% in one exam and 90% in another, it’s fair to say they are equivalent.
Conversely, if, on average, students in Number Two School who score 80% in their internal exams then achieve 50% in their external exams, then an 80% raw school mark from Number Two School will be treated as (i.e., “scaled to”) a true school mark of 50%. This adjustment accounts for the lower level of difficulty of Number Two School’s internal assessments (i.e., we can tell that they are “easier” because a student who only got 50% in the externals could get 80% in the internals - hence that 80% from Number Two School is actually worth less than a 70% from Number One school!
This is why it is beneficial to have a strong cohort - because the higher everyone in your cohort collectively achieves in the external exams, the higher your school mark will be worth! However, school rankings are usually measured by success rate, which refers to the proportion of Band 6s achieved by students in a particular cohort, not necessarily reflective of the full picture of a school’s academic standards and rigour!
Students, tutors, and parents need to adjust to focusing on a student’s ranking within a cohort (i.e., relative performance), rather than marks (i.e., absolute performance). Internal school marks are just a way to calculate an overall ranking within the cohort, which is what truly matters in obtaining a good school score.
For instance, let’s consider Jasper, who received 70% in his latest Year 12 Chemistry class test. While this mark may have been a cause for disappointment in Years 7 to 10, in Years 11 and 12, the focus should shift to how he performed relative to his peers. If the best scores in his cohort (who would later go on to score 95% in the external exams) were only around 75%, Jasper’s 70% would still place him in a high rank within his group. Therefore, he doesn’t need to worry, because his ranking won’t change significantly - in fact, he should be happy, because he did well considering the difficulty of the test! His bad-looking mark of 70 would actually be moderated to a school mark of around 92, which is excellent!
For an extra-technical look at how moderation works, we have to look at multiple students in one school doing the same subject. Conveniently, Rachel, Scott, Amelia, and Mohammed are all taking Business Studies at Number One School - so let’s take a look at their performances and see how their marks are moderated.
Moderation uses a student’s raw (non-aligned) external exam marks and actually involves students “swapping” their school ranks for corresponding external marks. This sounds weird - but it makes sense.
Let’s look at Rachel, Scott, Amelia, and Mohammed’s school rankings, raw external marks, and final external marks and how they’re used to produce a moderated school mark that makes up 50% of the HSC score. Don’t forget, alignment is done independently from moderation (in this case, we’re using a simple formula of +10, but in real life it’s more complicated).
| Student | Average school marks | School rank | Raw external mark | External rank | Aligned external mark | Moderated school mark |
|---|---|---|---|---|---|---|
| Scott | 80% | 1 | 75 | 3 | 85 | 95 |
| Mohammed | 75% | 2 | 85 | 1 | 95 | 90 |
| Rachel | 70% | 3 | 65 | 4 | 75 | 85 |
| Amelia | 65% | 4 | 80 | 2 | 90 | 75 |
After this process of swapping marks takes place, NESA then adjusts everyone’s marks according to the following four criteria:
Hopefully, you can see how the moderated school mark is derived from your internal rank assigning you an equivalent external mark by your equivalent rank in the external exams - it’s complicated but it makes sense once you realise how this is designed to only allocate school marks based on relative performance as cohorts get larger and statistics get more consistent. The more students with consistent high performances in school and in the HSC, the less likely you are to “swap” and “get adjusted for” for a mark that is drastically different to your abilities.
If you don’t fully understand the reasons behind this, never mind! Just know that if you score highly in school assessments, you get a higher school rank and hence your moderated school mark is based on a higher external HSC score that you or someone else got.
There are many takeaways from the moderation process:
Now we have a much better idea of how a student’s final school and external marks are calculated, we can better understand the two numbers that we use to make the average and hence calculate a final overall mark (HSC mark) and band for each subject.
But, you might be wondering, how do these marks get translated into an ATAR? Well, surely you’ve heard this before: the ATAR (which stands for Australian Tertiary Admission Rank, by the way) isn’t a score out of 100 produced by NESA, it’s a ranking! More specifically, the ATAR is a number between 30.00 and 99.95 that indicates a student’s percentile position relative to all the students in their age group. So, an ATAR of 80.00 means that you are 20 per cent from the top of your age group, i.e., you performed better than 80% of your age group, and an ATAR of 95.00 means you’re better than 95% of your age group.
Note that age group doesn’t mean HSC cohort - it includes people who started Year 7 with you but left high school in Year 10 to pursue vocational training, those who opted for the IB, and those who repeated or skipped a year! Therefore, the average ATAR is around 70.00 (and not 50.00 as you might expect statistically) - because the average person finishing the HSC is doing better than 70% of their cohort! You can’t get an ATAR of below 30.00 because the lowest 30% of each cohort almost always doesn’t complete the HSC and request an ATAR. You also can’t get an ATAR of 100 because you can’t be better than 100% of your year group - because you’re in your year group, and you can never have a score higher than yourself, even if you have the highest score!
Now, you might ask, since students can do so many different combinations of subjects, how do we compare different scores in different subjects together and make a final ranking of every student in the state?
Finally, we come to the most often misunderstood aspect of scaling - subject scaling. Many parents would have heard that studying subjects like Maths Extension 2 (4U maths) and Physics is “more worth it” than studying Visual Arts or Drama, but they don’t know why. Let’s clarify this!
Subject scaling is the process used to ensure that marks from different HSC subjects can be weighed fairly to calculate the ATAR. As we talked about in Article 1, you can’t compare a 70 in Maths Advanced or Chinese Beginners to a 70 in Maths Extension 2 or Chinese Literature - the latter two are much harder, and so a HSC mark of 70 (Band 4) in those subjects should be worth even more to the ATAR, separate to alignment.
Remember that alignment doesn’t measure subject difficulty relative to other subjects - it only measures subject difficulty relative to the bands of each subject! Alignment ensures a student’s mark reflects their achievement in bands (outcomes) for one particular subject but not in comparison to other subjects!
The underlying principle of scaling is that a student should not be advantaged or disadvantaged by choosing an “easier” or “harder” HSC course over another, not that their marks should be changed to reflect their band (alignment) or their school ranks should be assigned a consistent score aligning with students from their own, and hence all other, schools (moderation).
Subject scaling is not done by NESA - it’s done by UAC to produce the ATAR! It doesn’t affect a student’s HSC marks at all, but only how much each mark is worth relative to the same marks in other courses when ranking the student to calculate the ATAR. Let’s look at this step-by-step:
The HSC examination with the most candidates is the English Common Module Paper 1. This module is done by everyone who studies either English Standard or English Advanced, which is around 60,000 out of 70,000 HSC students each year. Hence, UAC is able to compare scores by using the Common Module as the “average subject” to benchmark scores in other subjects. For example, if, on average, students doing Science Extension and the Common Module paper got a much lower score on Science Extension, then it can be inferred that Science Extension is harder than the average subject. Conversely, if students doing Drama and the Common Module paper got a much higher score on Drama, then it can be inferred that Drama is easier than the average subject. By calculating the relative difficulty of each subject to the Common Module, UAC allows for equivalent scores in each subject to be directly compared to each other using “scaling curves”. These are the exponential-looking diagrams that you see everywhere - all you really need to know is that higher marks in “harder” subjects count for more, but the boost given by subject scaling diminishes as the student’s marks near 100.
TLDR: The harder the subject (compared to English Paper 1), the more a high mark will count towards the ATAR, though this effect diminishes as marks approach 100.
UAC then determines the top 10 units of a student’s HSC - i.e., counting only the best 10 units out of all the units the student studied throughout their HSC.
They first equate a student’s raw marks (not aligned marks!) in each of their subjects into a percentile performance in each subject. This is separate from the NESA-derived HSC marks. The percentile performances are then put through a series of very complex calculations, which we won’t cover here for simplicity (the exact details of which are covered in UAC’s ATAR technical report publication) to produce a scaled score out of 50 for each unit completed (100 for each 2-unit course). This scaled score is completely independent of the HSC mark, which is an average of the aligned external mark and the moderated school mark, but both marks are based on the same raw mark so nobody gets “cheated” of any scores or marks. Remember, HSC marks measure performance in each individual subject, while scaled scores (and ATARs) allow for direct comparison with other subjects.
Certain scores are then added to derive a score out of 500. This is instead known as an aggregate of scaled marks, and it represents the sum of scaled marks in 10 units of ATAR courses. This score comprises a student’s best 2 units of English and the best 8 units from all remaining units studied (including further marks in English if they are better than other marks). If a student did an odd number of subjects (i.e., 11, 13, or 15 units), then only half of a 2-unit subject may count towards the ATAR - meaning that a lower mark will only contribute half as much to the total score.
This score is never released to the public as UAC’s policy is to separate candidates only in increments of 0.05.
Finally, the score is used to rank students in an exact order and hence determine the final ATAR (ranking relative to age group peers), as we talked about above!
This is an even more complicated process than anything we’ve discussed so far (and many people think that it’s weird that the UAC score doesn’t actually come from the final HSC marks - but HSC marks only reflect how well you did in that individual course, and they don’t allow for comparison!). All you should take away from this process is that your external and internal marks in your best 2 units of English and 8 other units will always be scaled to compare to each other and then added to form a score out of 500 that is then used to derive your ATAR as a rank (rounded up or down to the nearest 0.05) which indicates that you scored better than 30% to 99.95% of your age group.
So, you might be wondering, how does alignment, moderation, and scaling affect my HSC strategy?
A strong support system can make the HSC more manageable. Working together with classmates and study groups allows you to share knowledge, stay accountable, and develop better learning strategies.
Healthy competition can drive improvement. The best students don’t just memorise information—they refine their problem-solving skills by comparing different approaches.
We also wanted to touch on something that hits close to home for many in the most competitive academic environments. Some students adopt a strategy called rank protection, where they focus more on maintaining a high rank than actually improving their skills. The idea is that a high internal rank can act as “insurance” in case of a poor external exam performance, while a low rank can negatively impact final results. However, rank protection is not a good long-term strategy - and, too often, it causes friction between friends, distrust within cohorts and school communities, and frustration at teachers and tutors.
If you ever find yourself being tempted to pick subjects simply based on scaling, thinking “I’ll just be grinding everything anyway, who cares what I pick”, or wishing you could advantage yourself at the expense of your cohort, remember two of JFK’s most famous quotes.
First, effort and courage are not enough without purpose and direction.
Second, and more important, a rising tide lifts all boats.
And when thinking of the HSC as a whole, a Churchill quote comes to mind…
We shall fight on the beaches, we shall fight on the landing grounds, we shall fight in the classrooms and libraries, we shall fight the notes and past papers and essays, and we shall never surrender…
Was that it?
See you in the next article!