When it comes to the ATAR, there’s a lot of stuff that’s left unexplained. Schools, teachers and parents tend to place an absurd amount of importance on your ATAR, as if it’s going to define the rest of your life, but then, nobody seems to understand how the system of ranking and scaling actually works.

For example, you’re told that if you’re really serious about getting a high ATAR, you should choose subjects like physics and chemistry, because they’ll scale your marks up.

On the other hand, subjects like art and music are said to scale your marks down. Beyond that, there’s a lot of complicated language and things don’t make much sense. And to be fair, it’s a freakishly complex system.

So we’re going to try to break down some of the main points. Here goes.

Raw Examination Mark

Your raw examination mark is exactly what it sounds like: the actual mark you got in your final exams. For some subjects, the exam might be out of 80, while for others, it might be out of 140.

Obviously it’s confusing to compare these marks, which is where your aligned mark comes in.


Your aligned mark (not to be confused with your scaled mark) is out of 100, so it’s a percentage. This is calculated from your raw examination mark and your school assessment mark. The two marks are aligned and the result is the examination mark and assessment mark that are printed on your record of achievement.

Aligned marks are a measure of how well you did with meeting the criteria of the syllabus, rather than how you well you did in comparison to your peers. This is totally different to your ATAR, which is a rank. So, depending on your subjects and your consistency across the board, a high aligned mark won’t necessarily mean you’ll get a high ATAR. This is because of ranking and scaling.

(There’s more info about alignment here.)


ATAR Scaling

Scaling is completely separate from aligning. Basically, scaling attempts to account for the differences in difficulty between subjects. For example, if you scored an aligned mark of 63 in STEM and an aligned mark of 63 in chemistry, scaling will most likely change those figures to account for their difference in difficulty between the two. Usually (but not always) a 63 in chemistry is going to be scaled higher than the 63 in STEM.

Why are some subjects scaled higher than others?

This is the burning question and it’s a controversial one. According to the UAC Scaling Report 2017:

“The model underpinning the scaling algorithm specifies that the scaled mean in a course is equal to the average academic achievement of the course candidature…”

It’s an absurdly complex sentence, but what it means (as far as we can tell), is that scaling is decided by the academic achievement of the whole cohort of students who undertook study in that course.

So, if the students who did chemistry all scored really high marks in all their other subjects, then a high mark in chemistry is deemed to be worth more than another subject where students predominately scored lower across the board.

This example from Dux College explains it pretty well:

“Suppose there were 9,000 Physics students and 9,000 Chemistry students, all of whom did English Advanced. All else equal, if the Physics students scored lower than the Chemistry students in English Advanced, then Physics will be scaled lower than Chemistry. The justification is that because Physics students didn’t do as well in their other subjects as the Chemistry students, a 90 in Physics is of lower achievement than a 90 in Chemistry.”

So scaling isn’t necessarily about how difficult a certain subject is, but how the students who do that subject perform in all their other subjects.

Essentially, subjects such as chemistry and physics are scaled positively because on the whole, the students who do physics and chemistry tend to do well in all their subjects.


So how is the ATAR calculated?

You probably know that your best ten units count towards your ATAR. For each unit, you receive a score out of 50; so for a 2-unit subject, this is a score out of 100 (your aligned mark).

When you add these marks up, you get a maximum score of 500. So after aligning and scaling, BOSTES calculates these scores and ranks students in order. You might be surprised to see how the scores are spread out.

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As you can see in the graph above, in 2016 only 8.3% of students score an ATAR above 95 and more than a quarter of students get less than 50. The rest are somewhere between.

The info in this article is just the tip of the iceberg. If you want to know more you can scope this article on ATAR Notes or this one from Dux College.