ATAR demystified

As Term 2 draws to a close many year 12 students are looking ahead to the Trial HSC exams. At Sandbox Learning Australia many of our students have been asking more and more about ATARs and the scaling process. It is a topic that is often misunderstood leading to confusion and anxiety.

In this article we will look into the ‘black box’ of ATAR calculation to show you how it works in a simple manner.

Summary

Don’t have time to read the whole article? Here are the key takeaways about ATARs and scaling.

  • ATAR is a RANK not a score

  • English has to count so it’s important to do well→ get help if you need it

  • Focus on what you can control: You can’t influence course scaling or how other students do

  • Internal assessments matter → you can’t just make it up in the HSC exams.

  • Assessment rankings matter more than the actual marks → pick up places where you can

ATARs, HSC marks and the difference between them

What’s an ATAR?

An ATAR (Australian Tertiary Admission Rank) number is a rank not a score.

It compares your performance against all other students who complete the HSC in your year. ATARs vary between 0 and 99.95 and increase in increments of 0.05. They are calculated by the University Admission Centre (UAC).

Since it is a rank your performance matters relative to everyone else. For example imagine that you score 90% on a test. Is that a good score?

  • Ordinarily you would say yes however imagine if there were 99 other students in your class and they all scored higher than you. In that case your rank would be last, e.g. an ATAR of 0.

  • If however the other 99 students all scored less than 90% you would be ranked first, e.g. an ATAR of 99+

Accordingly your ranks not your scores matter most.

When the HSC results are released you will receive a report from UAC like the one below,

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Example ATAR report from UAC for a fictional student

What’s the point of ATARs?

Universities use ATARs to select students for admission to university courses. This is a process of matching supply (number of places available per course) and demand (how many students want to get into a course). In general, courses where demand is much higher than supply require high ATARs, for example Law and Medicine.

While ATARs are still an important university entrance criteria, more universities are broadening their approach such as including personal essays and reviewing extra-curricular activities. While getting a strong ATAR certainly helps, it is not the be all and end all.

HSC Marks

The HSC mark in each subject indicates how well you performed in a particular course relative to the other students who completed that course. These marks are calculated by NESA (NSW Education Standards Authority, formerly the Board of Studies). As you’ll read ahead the HSC Mark is a mix of your internal assessment mark and your HSC exam mark.

6 steps to calculating your ATAR

At a high level there are six steps involved in calculating your final ATAR score.

  1. Moderate assessment marks

  2. Calculate HSC marks: 50% assessments, 50% exam

  3. Scale the HSC marks

  4. Add up the 10 best units including 2 of English

  5. Determine the ATAR ranking of the aggregate

  6. Round the ATAR to nearest 0.05

If you’d like the deeper information on scaling and ATARs check out the UAC scaling report.

Ok, here we go…

1. Moderate Internal Assessment marks

Schools use different internal assessments to each other. Naturally, some schools use harder assessments and others use easier assessments.

How do you know whether a 70% mark in School A is comparable to a 70% mark in school B? There needs to be a way to compare assessments across schools to compare apples with apples.

The answer is that NESA uses the performance in the HSC exams to ‘moderate’ the assessment marks.

What’s important to note is that while the assessment marks change, the ranks do not.

Let’s look at a hypothetical example below using a class of 6 students for one subject, e.g. English Advanced. The marks for both the school assessments (internal) and the HSC exam (external) are displayed.

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Hypothetical class of 6 students with assessment and exam marks

The first thing that happens is to set the moderated top assessment mark equal to the top exam mark. Since student A got the highest school rank they are given a moderated assessment rank of 92. In this particular case the 92 mark was their own mark, but regardless they would have been given the highest exam mark for the class.

Think about that again. If you rank first in your school you get the benefit of who-ever performs best on exam day.

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Second, the mean (or average) for the moderated assessment marks to set equal to the mean of the exam marks. Essentially UAC is assuming that the way students performed in the exam is a true reflection of their relative performance. During the exam students on average attained 68 while on internal assessments they attained 66. All else being equal this suggests that the internal assessments were a little harder than the HSC level and the assessment marks should be bumped up.

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Third (if possible) the moderated mark of the student ranked last is set equal to the lowest exam mark. This means that student F’s moderated assessment mark gets set to 50 — the exam mark achieved by student E. If the lowest exam mark had been 30, then student F would have received a moderated assessment mark of 30.

This is why is it really important to improve your rankings!

Sometimes this isn’t possible if the spread of the marks in the exam is really different from the spread in the assessments. In this case it is set similar to the lowest exam mark.

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Finally the rest of the moderated assessment marks are calculated so that it has a similar spread of marks to the school assessments, yet has an average equal to the average of the exam marks.

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Compare the differences between the moderated and unmoderated assessment marks for each student. Some students gain while others lose. It’s not able being fair, it’s just the stats!

Phew, after all that we now have the MODERATED assessment marks

2. Calculate raw HSC Marks: 50% assessments, 50% exam

This step is more straight forward. For each student you take a straight average of the exam mark and the moderated assessment mark, i.e.

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The table below shows an example for a potential student, let’s call her Anna, across 6 subjects.

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The HSC mark if the average of Exam Mark and Moderated Assessment Mark

Once we have these it seems like it should just be an exercise in adding up the HSC marks for the 10 best units right? Unfortunately no!

We have a similar problem to what we experienced in step 1. Looking at just these scores doesn’t tell us how easy or hard a subject is. Is 80 in English better or worse than 80 in Maths Advanced?

For that UAC needs to ‘scale’ the HSC subject scores. This is handled in steps 3 & 4.

3. Scale the HSC marks

Throughout Year 12 many students (and parents) get very caught up about scaling. This step is where scaling is put into action.

The purpose of scaling is to allow for an apples-to-apples comparison between subjects. It tries to answer the question “if all students undertook the same subjects, how would they perform relative to each other?”.

The first part of scaling the HSC scores is to work out your ranking in that subject. To do this UAC ranks all the students in that course from first to last based on their HSC mark. This determines your rank in the subject.

The table below demonstrates how the raw HSC scores translate in to percentiles for Anna.

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The same HSC mark can translate to very different percentile ranks

Using a bunch of statistics UAC converts the percentiles into scaled HSC marks. The chart below illustrates the relationship between percentiles and the scaled marks for the various English courses.

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Scaling curves for different English subjects in 2010

When people say that a “subject scales well” what they are talking about is that ranking highly in that course will translate to a higher scaled mark than a comparable ranking in another course. Looking at the chart above a student performing in the 90% percentile in English Standard would achieve a much lower scaled mark than a student performing in even the 90% percentile in English Advanced (or even the 50% percentile). Therefore Advanced scaled (much) better than Standard.

Statistically, the reason that certain subjects scale better is that on average better students take those courses. For example Latin Continuers isn’t a harder course than Business Studies. It is just that students who take Latin Continuers on average perform better in English and other subjects making it scale better.

With that said you have no control over which students take different courses and how they will perform. Because of this you can’t affect the scaling of different subjects. Instead of worrying about subject scaling, focus on what you can control which is how prepared you are for your own subjects.

Applying scaling to Anna’s raw HSC marks gives the following scaled marks.

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Converting raw HSC marks to scaled marks

Looking at the table you can see the effect of scaling by comparing the HSC marks to the scaled marks. For example the 79 in Maths 2U scales better than an 84 mark in Visual Arts (62.5 vs 54.8).

4. Add up the 10 best units including 2 of English

For the next step we need to add up the scaled marks for the best 10 units including at least 2 units of English. Unfortunately for Anna, her worst 2 units of scaled marks are in English Advanced. Based on her scaled marks, the 2 units of Visual Arts will not be included.

Since 2 units of English must count towards your ATAR, your performance in English matters disproportionately more that your performance in other subjects.

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ATARs take the 10 units with the highest scaled marks — but at least 2 must be English

Adding up the scaled marks give an aggregate total of 323.7

5 & 6. Determine the ranking of the aggregate and round

The aggregate number doesn’t really mean anything on its own. What’s important is how this number ranks compares to the rest of the HSC takers.

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How HSC aggregates convert to ATARs

Using the table above we can see that an aggregate score on 323 equates to an ATAR of just over 80. Actually ATARs are rounded to the nearest 0.05, e.g. 80.45

You can also do these calculations in reverse. To obtain an ATAR of 95 you will need an aggregate score of 404 or above.

So there you have it! Now you should have a better idea of how scaling works and how ATARs are calculated for each student.

Based on the above here are a series of takeaways,

Your English performance matters more than the rest of your subjects
2 units of English MUST be included in your 10 units. It is almost impossible to make up for bad English scaled marks with top performance everywhere else. If you are struggling with English don’t kick it into the too hard basket. Instead seek help from your school/teacher/tutor.

Assessment ranks matter more than the actual assessment score
The rank influences how your assessment score will be moderated. Fighting to jump up a few rank spots in each subject could mean the difference between getting the ATAR you want to not.

Help your schoolmates out
Once the internal assessments are out of the way it is in everyone’s interest to improve the exam mark mean. Increasing the exam mark mean will make your internal assessment look relatively hard and bump up the moderated marks.

Don’t waste time trying to game the scaling system
Subject scaling depends on how everyone in the state perform, over which you have ZERO control. Rather than wasting time thinking about how all your marks could scale, just do your best in every subject.

[For those in Year 10 or below] Pick at least English Advanced (vs Standard) and Maths Advanced (vs Standard) if you are going to do Maths
I completely agree that you should pick subjects that you enjoy. If you dislike a subject you won’t work hard and no amount of scaling with make up for that. However when it comes to the level of a subject that’s a different matter. English Standard/ESL and Maths Standard (previously General Maths) scale so much worse than the Advanced courses that if you can even just manage in the course you should.

The counter to this is where you want to continue doing maths but don’t want to learn calculus (and you don’t need it for further study) AND you will be doing 12+ units. The Maths Standard course contains much more practical maths than the other calculus heavy Maths courses and so it a good course for real learning. However if the goal of the HSC is to get a high ATAR 90+ then Maths Advanced is strongly preferred.

That’s it for now. Happy learning!

Jesse Whelan is the Founder and Director of Learning at Sandbox Learning Australia. He is passionate about helping children maximise learning by using effective long term strategies.

Do you, your child or someone you know need maths help? At Sandbox Learning Australia we use the science of learning to deliver coaching that is both personalised and effective.

If you are in Sydney please contact us to arrange a free baseline assessment of your child’s strengths and weaknesses.