This article is modified with permission from this forum thread, now archived. It was written by ATAR Notes user “Joseph41”, and all information in this article is based on that user’s experiences and interpretations.

 

In 2018, Australia’s then-Chief Scientist, Dr Alan Finkel, suggested the ATAR is “completely obscure” and “is leading to students being given poor advice” in regard to their subject selection at high school (read here).

I think it’s true that the ATAR and the technical side of VCE isn’t that transparent. It’s generally not taught explicitly in schools, it’s confusing for students and families, and I’m quite sure it leads to a lot of unnecessary anxiety through high school.

The point of this article is to try to allay some of those concerns, and to spell out clearly how the VCE system works from a technical point of view.

It’s important to note that nothing in this article is crucial knowledge in order to score highly. You don’t need to know it to do well, and you similarly aren’t guaranteed good scores by knowing it. Instead, the value comes in the idea that once you know how the system works, you don’t need to worry about it, and can instead focus on things you can control - like how you study!

So - let’s start from the start.

 

What is an ATAR?

The ATAR (Australian Tertiary Admission Rank), renamed in 2010 from the ENTER (Equivalent National Tertiary Entrance Rank), is a number calculated by VTAC to allow tertiary institutions to compare students’ levels of performance across subjects (read more from VTAC). Universities and other tertiary institutions can use the ATAR as one criterion - but not the only criterion - for entry into various courses.

ATARs are reported between “less than 30” and 99.95, which is the maximum ATAR. There is a minimum increment of 0.05 (so 30.00, 30.05, 30.10, 30.15… 99.80, 99.85, 99.90, 99.95). No ATAR ending with anything other than a second decimal place of 0 or 5 exists.

The ATAR does not reflect your raw marks. That is, an ATAR of 80.00 does not indicate you have averaged 80% across the year, nor does it indicate you achieved 80% on your exams. Instead, it suggests VTAC deemed you to have outperformed 80% of your cohort (those with whom you started Year 7) - it’s a percentile ranking.

VTAC explains the ATAR as “the estimate of the percentage of the population in the relevant age group that the student outperformed”. That is, where you ranked in your cohort - not your raw marks on tests (or SACs) and exams. It’s for this reason that you can’t achieve an ATAR of 100; you can’t outperform 100% of your cohort (which includes yourself).

It’s important to note that the ATAR is not the only way to gain entrance into tertiary education, and it’s certainly not make-or-break. This largely falls outside the scope of this article, but you should know that the ATAR is just one key to a door. It’s not the only key.

 

How is the ATAR calculated?

As you can probably imagine, it’s quite difficult to establish how well a single student has performed in the context of the entire state. Why? Because that student will be exposed to different subjects, different SACs (School Assessment Coursework - more on that later), and different stringency of marking throughout the year.

Different SACs and different approaches to marking both threaten a fair system.

Naturally, VCAA wants a fair playing field, and doesn’t want to unjustly advantage or disadvantage any student. For this reason, we can’t just say, “we’ll add up all of your scores throughout the year, and rank you that way!”, because that wouldn’t necessarily be a true indication of students’ achievement.

As such, we need a more objective way of ranking students across subjects and conditions, and for this, we use the aggregate.

 

The “aggregate”

Very many students are aware of the ATAR; many fewer are aware of the aggregate.

According to VTAC, “[t]he aggregate is a number between - and a value that can reach over 210”. As above, your aggregate is what VTAC uses to rank you against other students in the state. You can picture it as your “ultimate high score”, with each study score being analogous to your high school for an individual level of a game.

So, how is the aggregate calculated, exactly? Remember, we need this to be able to work out each student’s ATAR.

 

How is the aggregate calculated?

Your aggregate is basically the sum of:

• your highest-scoring English subject (English, English Language, Literature, or English as an Additional Language);

• your next three highest-scoring subjects; and

• if applicable, 10% of your fifth and sixth highest-scoring subjects.

 

So to clarify, a maximum of six subjects can count toward your ATAR. Your top English subject plus your next three best subjects form your “top four” or “primary four” (read more here); you might hear your fifth and sixth subjects referred to as your “bottom two”. The top four/primary four subjects are required in order to receive an ATAR; the bottom two are not.

Anything beyond the sixth subject (so, say you studied a seventh, eight, ninth etc. subject) is not considered toward calculation of the ATAR (see more). That’s not to say you absolutely shouldn’t study more than six subjects, of course - there are reasons to do this, including but not limited to personal interest, and prerequisite subjects required for admission to a course or pathway. 

 

A quick note

It’s not only Units 3&4 VCE subjects that can count toward your ATAR. You also have the option of:

• “Higher Education Studies” (colloquially, uni extension subjects), which can count as either your fifth or sixth subject, but cannot count toward your top four/primary four. An increment of 3.0 - 5.0 inclusive is awarded depending on your achievement in that subject. More information can be found here, on page 7.

• Alternatively, there are VCE VET sequences (either scored or unscored). The processes for unscored VET subjects are a little different, but they essentially add to your ATAR based on your other study scores. More information can be found here, also on page 7.

 

Aggregate example

So, let’s demonstrate how the top four/bottom two functions in practice. Let’s take an example of Joseph (he/him), who studies seven VCE Units 3&4 subjects. Note that these subjects don’t need to be completed in Joseph’s year of graduation in order to contribute to his ATAR.

Joseph’s subjects, plus his final scaled scores (more on this later), are listed below in alphabetical order (for all intents and purposes, you can picture study scores as ‘out of’ 50, but in practice, these are also rankings):

• Biology: 46

• Chemistry: 25

• Health & Human Development: 49

• Literature: 28

• Physical Education: 33

• Specialist Maths: 42

• Studio Art: 30

 

If we order these from best to worst, we’re left with:

• Health & Human Development: 49

• Biology: 46

• Specialist Maths: 42

• Physical Education: 33

• Studio Art: 30

• Literature: 28

• Chemistry: 25

 

But remember that an English subject has to be included in the top four. Let’s put Literature (Joseph’s only English subject) right to the top by default:

• Literature: 28

• Health & Human Development: 49

• Biology: 46

• Specialist Maths: 42

• Physical Education: 33

• Studio Art: 30

• Chemistry: 25

 

From these scaled scores, we can now calculate Joseph’s aggregate. Remember, that’s the top four subjects (including an English subject), plus 10% of the fifth and sixth subjects if applicable. So in this case, that would be:

28 + 49 + 46 + 42 + 3.3 (10% of Physical Education) + 3.0 (10% of Studio Art) = 171.3.

Note that the score of 25 for Chemistry doesn’t count at all, because it was Joseph’s seventh best subject. In summary:

 

Conversion from aggregate to ATAR

Now, this aggregate of 171.3 probably doesn’t mean much to you - nor should it, because aggregates are rarely spoken of or considered, even in VCE circles. But what now happens is all aggregates are ordered, giving VTAC a way to rank students, irrespective of which subjects they took. Each student, based on their aggregate, is then attributed a percentile rank, and this percentile rank is converted to an ATAR.

How do they do this? Well, they have what’s called an “aggregate to ATAR conversion table”. It is how it sounds - it just shows what minimum aggregate is needed in order to achieve whichever ATAR. You can find the 2017 aggregate to ATAR table here. You can find a general idea below, but note that the figures will vary from year to year.

 

Restrictions on the ATAR

Just a quick note here: there are a couple of other things that might affect you and your ATAR. For example, there is a limit to the number of similar subjects that can count toward your ATAR. VTAC says:

“There are some restrictions on how certain combination of studies may be counted for an ATAR.

In each of the study areas of English, mathematics, history, contemporary Australian studies, information technology, languages and music:

• at most two results can contribute to the Primary Four

• at most three results can contribute to the ATAR, the third being counted as a 10% increment for a fifth or sixth subject

This also includes Higher Education studies.”

 

So, let’s say you’re studying the following subjects, and get these scaled results:

• General Maths: 50

• Maths Methods: 44

• Specialist Maths: 42

• Biology: 41

• English: 36

• Uni Extension Maths: 3.5

 

In this case, there are four maths subjects (Further, Methods, Specialist, and Uni Extension). Even though the first three are your best three subjects, only two of them can count in your top four. And because only three maths subjects can count toward your ATAR, the uni extension subject won’t count at all. Basically, the situation would be:

• English: 36 (top 4)

• General Maths: 50 (top 4)

• Maths Methods: 44 (top 4)

• Biology: 41 (top 4)

• Specialist Maths: 4.2 (10% increment)

• Uni Extension Maths: N/A

 

So now we know that your ATAR is determined by your percentile rank, and that your percentile rank is determined by your aggregate. We also know that your aggregate is the sum of your study scores (with stipulations), which leads us to the question: what is a study score, exactly?

 

What is a study score?

A study score is sort of like a mini-ATAR: it’s a standardised ‘score’ from 0-50 that you’ll receive for each of your individual subjects. The median study score is 30 (see page 8 here).

Like with the ATAR, though, study scores aren’t really scores at all - at least, not in the traditional sense. Again, they’re rankings of how well you’ve performed in the context of the cohort for that subject. A study score of 40, for example, certainly doesn’t mean you’ve averaged 40% (or even 80%, given study scores are only out of 50).

Study scores are standardised, meaning they work on a bell-curve. The standard deviation is about 7, meaning that approximately two-thirds of students in a subject will receive between a 23 and a 37 study score inclusive. Anything below a 23 or above a 37 is more than one standard deviation away from the median study score of ~30. I’ve modified this image below to show the standard distribution, with some study scores in red.

 

How are study scores calculated?

The basic process is this:

• You are awarded a letter grade (from E to A+) for each Graded Assessment. There are three Graded Assessments (or GAs) per subject. These will change from subject to subject. For example, for General Maths (a subject with two exams), GA1 refers to overall SACs, GA2 is the first exam and GA3 is the second exam. For something like Psychology (just the one exam), GA1 refers to Unit 3 SACs, GA2 is Unit 4 SACs, and GA3 is the exam.

• These scores all contribute to a ‘total score’ of sorts, which is standardised (against the bell-curve mentioned earlier), taking into consideration things such as weighting (as not all GAs are worth the same amount).

• The score is converted to be out of 50.

 

The standardisation means that, every year, the distribution of scores is pretty close to the image below. See here for more details.

As you can see, only ~9% of students receive a study score of 40+, and only ~2% of students receive a study score of 45+. To receive a study score of 30, you need to be in the top ~half of the cohort.

What this means is that, in theory, you probably could roughly predict your study scores if you had all of the necessary information (as you could roughly work out how many standard deviations you were from the median). Personally, I think this is a poor use of your time. I know it can be frustrating not really knowing where you sit but, ultimately, intricately going through the system and trying to predict your scores won’t actually increase them. Studying might, however, so that’s a much better use of time!

Now, you might be thinking, “okay, cool - but not all SACs are the same; how is that fair?” Well, it wouldn’t be if we didn’t have SAC moderation. Luckily, we do!

 

SAC moderation

VCAA wants a fair system. The current system reflects that; it has been devised in a way that aims to eliminate all unfair advantage or disadvantage given to any particular student. As you can no doubt imagine, there are a couple of things that threaten the fair system that VCAA is hoping for.

One of these is the fact that different schools have different SACs, and could, therefore, give out extremely easy or extremely difficult tests compared with the VCAA standard. For example, my school might give really easy SACs, and the school in the next suburb might give very difficult SACs. This would obviously be to my advantage - it would be easier for me to get a good mark than students at the other school.

Another potential flaw in the system is the idea that teachers mark differently. Even if, hypothetically, every school in the state administered the same SACs (which isn’t the case), we’d still face the issue that some teachers mark stringently, whilst others are more lenient. It would be unfortunate to lose points from your results just because of the way your teacher marked, and VCAA knows this very well.

As such, VCAA aligns (or moderates) each school’s SAC results to be more in line with VCAA’s own standards. Let’s consider a few different examples.

We have three different schools here: School A, School B, and School C.

Throughout the year, students from School A received a median mark of 50% on their SACs. But in the end-of-year exam, the median mark for that cohort was much higher: 75%. What this suggests is either that School A’s SACs were more difficult than VCAA’s standard, or that they were marked too harshly. This wouldn’t be fair on the students from School A, so VCAA boosts their collective SAC marks accordingly.

Throughout the year, students from School B received a median mark of 80% on their SACs. But in the end-of-year exam, the median mark for that cohort was much lower: 50%. What this suggests is either that School B’s SACs were easier than VCAA’s standard, or that they were marked too leniently. This wouldn’t be fair on other students who sat more difficult SACs, so VCAA lowers School B’s collective SAC marks accordingly.

School C’s median SAC mark and exam mark is about the same, so VCAA makes no change; those SACs already seem to be reflective of VCAA’s standard. Directly from VCAA:

“Students now have moderated School-based Assessments, which are comparable across the entire VCE system. For example, if we compare moderated School-based Assessments in Geography, we can be sure that a student in Horsham with a mark of 75 has a higher achievement than a student in Richmond with a mark of 60. Before moderation we would not have been able to tell which student had the higher achievement because they are on different scales…”

Comparing SAC marks before moderation just isn’t logical. In the same way, consider two tubs of bricks. One weighs 50 kilograms, and the other weighs 100 pounds. It’s illogical to say that the second tub of bricks is heavier just because 100 is greater than 50; we can’t really compare them, because they’re set on different scales (kilograms and pounds). When we convert them both to the same measurement scale, we can actually see that 50kg is heavier than 100lbs, but we couldn’t tell that until we’d moderated the scale.

That’s exactly what VCAA is doing with SAC moderation. Comparing your raw SAC marks with people you know from other schools is a pretty fruitless exercise. It’s a little more complicated than that, as indicated by the quote below, but that’s the basic premise. From VCAA:

“[T]he following marks are determined for both the School-based Assessment scale and the external score scale: the highest achievement, the upper quartile, the median and the lower quartile.³ These scores are used as fixed points for aligning the two scales…”

The other take-home point here is that, really, it’s in your interest for your cohort to perform well in the exam(s), and trying to sabotage your cohort’s marks is really just sabotaging yourself.

Where it gets really interesting, though, is that this sort of thing also happens on an individual level, and that’s what we’ll look at now in the form of rankings. Also note that these raw study scores don’t consider the competitiveness of that subject in that given year. We’ll consider this in the “Subject scaling” section later on.

 

SAC rankings

You might have heard that “it’s not really your raw marks that matters; what matters is your ranking”. What does that mean?

Well, throughout the year, a hierarchy is established within your cohort for SAC performance. That is, the student in your cohort with the best SAC average will be rank #1, the next best average will be rank #2, and so on. A lot of things can change through SAC moderation/scaling etc., but SAC ranking is not one of them. If you finish as rank #1, you’ll stay as rank #1.

“[T]he rank order of students’ assessments in a school is not altered by statistical moderation… The VCAA acknowledges that teachers are in the best position to measure students’ academic achievement in School-based Assessment.”

VCAA

 

Having a high rank is important because it means you benefit from your cohort’s exam performance. This is most easily explained with an example.

(Please note that the following section is very rough, and in reality it doesn’t work as neatly as this. Having the second highest ranking doesn’t necessarily mean you’ll get the second highest exam mark as your SAC mark etc. - it’s just an easy way to explain the basic process. ACtually considered are gaps between ranks and other factors, so keep this in mind.)

Okay, so there’s a bit to take in here. Basically, this table shows a cohort of 10 students studying one subject. It doesn’t matter which subject. The students are listed by SAC ranking - Student A had the highest average, Student B had the next highest average, then Student C, and so on. It also shows each student’s end-o-fyear score on the VCAA exam.

What you might notice straight away is that the best-performing students from throughout the year in this cohort didn’t actually perform the best on the exam, as may be the case in reality. To run you through what happens briefly:

• Rank #1 gets the best exam score as their moderated SAC score. In this case, Student A achieved a 52% on the exam, but benefitted from Student D’s 99% as they’re rank #1. Student A’s exam score isn’t affected, but they get 99% as their moderated SAC score.

• Rank #2 gets the second best exam score as their moderated SAC score. In this case, Student B achieved a 96% on the exam, which just happened to be the second best score of their cohort. As such, their moderated SAC score is 96%.

• Rank #3 gets the third best exam score as their moderated SAC score. In this case, Student C achieved an 89% on the exam, which just happened to be the third best score of their cohort. As such, their moderated SAC score is 89%.

• Rank #4 gets the fourth best exam score as their moderated SAC score. In this case, Student B achieved a 99% on the exam. However, as this was the best exam score of the cohort, it actually goes to rank #1 in terms of moderated SAC score. Student D gets allocated 85% as their moderated SAC score, as this was the fourth best exam score in the cohort.

 

As you can see, having a high SAC ranking can be a pretty big advantage. If you’re stuck near the bottom of your cohort, your moderated SAC score is, at least to a degree, a little contingent on exam performance of those ranked above you.

Now, once all this has been said and done to find your raw study scores, they get scaled according to ‘competitiveness’. Let’s explore that further.

 

Subject scaling

As we know, VCAA is looking for a fair system, and a big consideration in that is how to compare vastly different subjects. For example, how can you really compare Visual Communication & Design, and Chemistry? That would be very difficult, indeed.

The idea is that the raw scores you receive don’t actually take into account how difficult it was to achieve a mark in the middle of the cohort in various subjects. For clarity - and this is something VCAA also stresses - by “difficulty”, I don’t mean how complicated the content is. After all, that’s an extremely subjective measure. Instead, “difficulty” here is measured by competitiveness in the subject.

“All Study Scores are scaled to adjust for the fact that it is more difficult to obtain a high Study Score in some studies than others. This is NOT because some studies are inherently harder than others. This IS because some studies attract a more competitive cohort of students than others.”

VCAA

 

This is the reason that subject scaling changes a little from year to year - not because VCAA is arbitrarily changing its mind on how difficult subjects are, but based on varied competitiveness in subjects from cohort to cohort. There is nothing inherently about Specialist Maths that means it scales up, and it could just as easily scale down if the cohort were right. Similarly, Health & Human Development could scale up if the cohort were right.

Now, how is “competitiveness” measured? Basically, it’s measured by how well students in a particular subject do in their other subjects. This might seem a bit counter-intuitive, but let me explain it in this way.

Say you’re going to compete in two different 100-metre races. In the first, you’re up against a bunch of slow non-athletes. In the second, you’re up against Usain Bolt, Tyson Gay, Yohan Blake, Asafe Powell, and a bunch of other professional sprinters. Neither of these races is inherently more difficult - they’re both simply a 100-metre running race. But the competition is vastly different, thereby making it much easier to achieve a mid-place ranking in the first race than the second.

The competition, here, is determined by how well the competition does in their other races. So, Bolt, Gay, Blake, Powell etc. are, on average, going to do very, very well in their races. This is probably not the case for the non-athletes from the first race. The same sort of principle holds with the VCE system.

According to the 2017 scaling report, English Language scaled from a raw 30 to a scaled 33. How did that happen? Well:

• We consider all of the English Language students studying the subject that year.

• We look at how those students have performed in all of their other subjects.

• We take whatever the English Language students averaged in all of their other subjects, and that becomes the new average for English Language.

• So, in this case, it was determined that the English Language cohort performed above the average by about three points, which is why the subject scaled up by three.

 

Equally, we could look at, say, Geography, which scaled from a raw 30 to a scaled 29.

• What we can extrapolate from this is that Geography students, on average, scored a 29 for their other subjects.

• And the average study score for Geography, therefore, has been scaled down by one to account for this below-average competitiveness.

 

Some people see subject scaling as ‘rewarding’ or ‘punishing’ those taking certain subjects, but it’s simply not the case. All VCAA is doing is levelling the playing field. Without this scaling, those studying subjects where it’s more competitive and, therefore, more difficult to achieve a middle ranking, would be unfairly treated.

With this in mind, the best thing you can possibly do is choose subjects you a) need as pre-requisites for your university course or other pathway; b) are passionate about, and c) are good at. There is no way to “game” the VCE system in this way.

 

Closing remarks

To reiterate, everything here is based on my understanding of public documents, and there will be intricacies I’ve not covered or explained. None of the information is required in order to do well. However, I hope that the article has been helpful and will, ultimately, give you the peace of mind to focus instead on your study.

Best of luck!