ATAR Explained – How the ATAR is Calculated

ATAR Explained – How is the ATAR Calculated?

This article was written by Sam Daffy, a VCE Specialist Maths tutor. You can see more about Sam’s tutoring services here.

A lot of parents and students don’t really get the ATAR. And frankly, I don’t blame you – it’s quite convoluted, but hopefully, this will help.

Before we get to the ATAR, let’s start with the subjects. Each VCE subject consists of four units, and each unit takes two terms (half a year). So the four units take two years, which is why most VCE subjects are done over Years 11 and 12. The bit that affects your ATAR is units 3 and 4, which is mostly done in year 12. A lot of students do one or two ‘year 12’ subjects (units 3 and 4) in year 11 to get a taste of what SACs and VCE exams etc. are like. This is probably a very good idea, even though I didn’t do it myself.

So within each subject, for units 3 and 4, there is school assessed coursework (SACs) and at the end of the year, there’s an exam. Some more hands-on subjects have school assessed tasks (SATs) as well as SACs. Every subject has at least one SAC, but there’s a fair bit of variation between subjects. The SACs and especially the exam contribute to the study score for the subject.

So these SACs, SATs and exams combine to give you a score out of 50, right? Wrong. It’s a bit more complicated than that. Every student within each subject is ranked, then given a score according to a bell curve (called the normal distribution), as shown below:

Above: The complicated yet normal distribution of study scores

So the average score for each subject is 30, with 68% of all students getting between 23 and 37, and these scores go all the way up to a few students getting 50, and in theory, all the way down to 1.

So that’s subject scores done, right? Not quite – next we come to scaling. There are two types of scores to think about – the ones I’ve just described are called raw study scores, but then these are scaled and they become scaled study scores.

Note: the following information below was added in by Alex Niehof, a VCE Specialist Maths tutor. You can learn more about Alex’s services here

Subject scores are scaled based off a complicated formula used by VTAC (Victoria Tertiary Admissions Centre) to make sure students picking easy subjects aren’t advantaged, and students picking difficult subjects aren’t disadvantaged. The scaling system loosely works like this:

Let’s imagine there are 100 Specialist Maths students in Victoria who also do English, and of these 100 students, exactly 10 of them get a 30 in Specialist Maths. VTAC then takes the English results of all 10 of these students and finds the average of them. For example, if of the 10 students who got a 30 in Specialist, they returned English results of; 43, 36, 49, 41, 46, 35, 40, 38, 45, and 47. The average of those is then taken; 42.

VTAC then uses this analysis to determine that students who achieve a 30 in Specialist Maths achieve on average a grade 12 points higher in English. They then scale up all 30 study scores in Specialist by 12 more than they scale up English. The same process is then completed for all 50 different study scores for every pair of subjects. In this scenario, they may determine that on average an English score of 30 scales down 1 compared to other subjects, and on average, a Specialist Maths score of 30 scales up 11 compared to other subjects. So Specialist will scale up 11 if you get a 30, and English will scale down if you get a 30, which corresponds to the calculation in the previous paragraph, where we worked out that the difference in scales between the subject must be 12.

This complex process generally succeeds at working out which subjects are hard, and which are easy. For example, In Year 12 I did all 3 VCE mathematics subjects, and they all scaled to within 1 study score of each other, so the process worked in that regards. However, the scaling system relies on a core assumption, that each student tries equally hard for all their subjects and are equally capable in all of them, and therefore any variations in study scores must be due to differences in difficulty.

There’s a couple of key exception to this assumption which goes a long way to explaining why a lot of students feel their subject has been scaled unfairly. The first involves folio subjects, such as VCD and Food Technology. Folio subjects typically require an enormous amount of time over the year, particularly toward the end of term 3 when folios are due. As a result, many folio students partially neglect their other subjects out of necessity, which lowers their result in other subjects. VTAC notices that students typically do better in folio subjects than their other subjects, (through their calculation) and scales down folio subjects accordingly, even though they’re not easy, people just put a lot of effort into them. The other exception is around common pre-requisite subjects such as Methods and Science subjects. Students pick these even though they don’t play to their strengths or interests because they’re effectively compulsory for their university pathway. As a result, these students perform worse in these subjects than the rest of the cohort choosing them because they enjoy them. This lowers the average performance in these subjects relative to other subjects. VTAC then judges them to be harder than other subjects (often they are, but this generally overstates the difficult gap) and scales them up. This goes a long way to explaining why science and maths students typically gain a lot in scaling compared to humanities focused students. 

In addition, some subjects, like languages other than English, are given extra scaling because the government wants to give students an extra incentive to study them.

VTAC then takes the best English scaled study score that you have (typically English), as well as your next 3 best scaled results and adds them together. If you have 5th and 6th subjects, VTAC takes 10% of both of these and adds them to the original result. If you have 7 or more subjects completed at a 3+4 level, any additional subject beyond your best 6 won’t contribute to your ATAR.

This sum, the top English result, plus the next top 3 and 10% of 5th and 6th subjects, then becomes your ATAR aggregate. Your ATAR aggregate is then ranked against the aggregate of every other student graduating in that year in Victoria. This ranking gives your ATAR, on a scale from 0-99.95. It can’t be 100 since it’s a measure of the percentage of students you beat, and you can’t be better than everyone including yourself.

*ATAR aggregate is what is used for subject bonuses, SEAS and other university admission schemes. If a university decides to award you 2 aggregate points for getting, for example, a 30 in Chemistry, a 2 is added to your ATAR aggregate and your ATAR is then recalculated. Typically, if your new calculated ATAR is over the ATAR requirement for that subject, you’ll now get in. 

**ATAR aggregates are roughly twice your ATAR. For example, my ATAR aggregate was 185.67 and my ATAR itself was 98.00. Better approximations can be found through services such as ATAR calculator.

Subject scores are scaled because some subjects are seen as harder than others. For instance, Specialist Mathematics scales higher than Mathematical Methods. Every year the scaling for each subject is slightly different, but it doesn’t usually change too much. So some subjects, like Specialist Mathematics, scale up so that if your raw score in 2015 was 30, your scaled score would be 41. Other subjects like English don’t scale much at all, while some subjects, like Further Mathematics, actually scale down, so that if your raw score in 2015 was 30, your scaled score would have been 27. This is meant to balance out the fact that some subjects are harder than others to do well in. Some subjects, like languages other than English, are given extra scaling because the government wants to give students an extra incentive to study them (in this case so that we can do business etc. with people from overseas who don’t speak English).

So once you get all your scaled study scores, including from any Unit 3 and 4 subjects that were taken in Year 11, they are added up and the number that comes out the other end is your aggregate.

Then, once again, each student is ranked, except this time it’s against every other Year 12 student in Victoria. And finally, you get your ATAR, which can be anywhere from 0 to 99.95. It can’t be 100 because it’s a measure of the percentage of students you beat, and you can’t be better than everyone including yourself.

So that’s the complicated, technical thing that is the ATAR system. To summarise, your SACs, SATs and Exams become your study scores (raw then scaled), which then become your ATAR.


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ATAR Explained – How the ATAR is Calculated

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