HSC ATAR Scaling Report - How does NESA and UAC scaling work?

Curious about NESA and UAC HSc Scaling? This article goes through the ins and outs of HSC scaling and exactly how the ATAR works - keep reading to find out!

a month ago   •   8 min read

By KIS Academics
Photo by Matese Fields / Unsplash

HSC Scaling can be difficult to wrap your head around when entering the final year of high school. KIS Academics aims to assist students in achieving their best results, which can be maximised with a good understanding of this process and how ATARs actually work!

So how does this work? To calculate your final HSC mark for each subject, 50% of your mark is your HSC exam score, with the other 50% being your moderated internal assessment score. Both your HSC exam scores and your internal assessment scores will be moderated and adjusted according to different factors, which will be explained below!

Internal exam marks:

Each subject will provide a minimum of 3 assessments throughout year 12, each weighted accordingly which will provide you with an overall average mark after completion of the final internal assessment, HSC trials.

Rankings are provided relative to your school’s cohort for each subject. These raw internal marks are NOT what you are assigned as your 50% weighted internal score, which is where many people get confused! These marks are scaled according to your individual ranking compared to peers at your own school, and your school’s performance relative to the whole state.

The easiest way to understand how scaling works between different schools is by comparing raw marks to HSC marks. For example, let’s say School 1 provided a Maths Advanced average internal assessment mark of 80 and School 2 provided a Maths Advanced average internal assessment mark of 60.

Now let’s say students from both schools scored an average mark of 70 in the final HSC exam. It would be unfair to provide School 1 students higher overall averaged marks for Maths Advanced as their actual performance in the final exams displayed equal performance/ability as School 2.

Performance in internal assessments varies across schools according to a variety of factors, such as individual student performance, varied marking of assessments and varied assessment difficulty. As such, NESA adjusts the marks awarded for the internal component of the final subject mark according to the performance of schools across the state.

This is undertaken through a statistical algorithm. The outcome of this scenario would involve School 1’s internal assessment marks being scaled down from 80 to a lower mark, to reflect their lower performance in the HSC relative to the internal marks submitted to NESA.

Similarly, School 2’s internal assessment marks would be scaled up to reflect their better performance in the HSC relative to internals. This reflects School 2 likely provides more difficult assessments throughout the year compared to School 1.

The way this looks for individual students is by adjusting the mean of a school’s assessments to match the mean of that school’s final HSC exam marks.

Then, the top HSC internal assessment mark is adjusted to match the highest HSC exam mark, no matter who achieved the highest mark in the final exam.

Similarly, the bottom moderated HSC assessment mark is adjusted to match the lowest HSC examination mark achieved by whichever student in the school’s cohort achieved the lowest mark. This is not a hard and fast rule, however, as there are situations where the distribution of marks across internal exams and HSC exams vary too much to provide exact equivalence.

As such, the bottom moderated marks may be adjusted up or down to ensure fair and proportionate moderation.

For instance, this prevents someone who achieved the lowest internal assessment rank, from being assigned a disproportionately low moderated mark due to an unexpectedly poor final exam performance by another student in the school group.

For example, let’s say person A ranked 1st in the internal HSC assessments, and person B ranked 2nd. But, in the final HSC exam, person B achieved a score of 96 and person A achieved a score of 90. This means person A would receive person B’s score of 96 as their INTERNAL ASSESSMENT score as they ranked first throughout the year in their assessments.

Subsequently, person B would receive person A’s (90). Remember, everyone’s individual HSC EXAM score is not adjusted based on the school cohort. This is explaining how the internal exam marks are moderated to reflect the school cohort’s performance in the final exam.

To get the full picture, this is how person A’s score would be calculated with a moderated internal assessment score of 96 and a final HSC exam score of 90:

Person A final HSC mark = (Moderated Internal Assessment Mark + HSC Exam Mark) / 2

= (96 + 90) / 2

= 93

HSC marks:

Scaling by subject is another key concept to understand. Some people will recommend certain subjects as they ‘scale well’ and may discourage others from ‘scaling badly’.

Other people recommend choosing the subjects that you enjoy the most, as you will likely perform best in those as opposed to choosing a subject purely for its scaling benefits. To make the best and most informed choice, it’s important to understand the standardisation of subjects and why it happens.

Subject scaling is necessary to reflect the relative difficulty of the exams and the capability of student cohorts across different subjects. The easiest comparison to make is between Standard English and Advanced English.

Your performance in the HSC exam is calculated as a raw mark, generally out of 100 for a 2-unit subject. If the state provided an average HSC exam mark of 80 in Standard English and 70 in Advanced English, it would be unfair to award these marks as raw contributions to the ATAR calculation process.

This is due to the greater difficulty of the Advanced course, alongside the greater English capability of students undertaking the Advanced course. The final exams of more difficult courses are formulated to be more difficult by examiners to reflect the higher level of ability. The same concept applies when comparing English Advanced to English Extension I and English Extension II.

The performance of cohorts across all subjects is compared and scaled to reflect the strength of students undertaking different courses. As such, the raw marks a student gets in a specific subject will be scaled up or down depending on the performance of the overall subject cohort and their performance across various subjects.

This breaks the myth that ‘easier’ subjects are easier to get band 6s in, as fewer band 6s are awarded to the subjects that are ‘scaled down’.

For example, the greater difficulty of English Advanced compared to English Standard will cause the distribution of marks in English Advanced to be scaled up, with a greater proportion of those students being awarded band 6s.

Comparatively, English Standard will have a lower distribution of overall HSC marks after scaling due to the lesser difficulty of the subject and the lower relative ability of students undertaking the course compared to English Advanced, Extension I or II.  This will cause a lower proportion of English Standard students to be awarded a Band 6 as fewer of the students will have a final scaled mark of above 90.

A key message is to not take your raw internal marks too seriously (within reason!). You may be disappointed with a seemingly low raw internal mark in a subject such as Physics.

However, this mark will be adjusted according to scaling factors and will likely increase due to the relative difficulty of assessments in the subject and the likely overlap of students performing highly in both physics and other high-scaling subjects, such as Extension I and II Mathematics.

This elevates the scaling of Physics and would cause HSC marks, and hence internal marks, to be scaled up to reflect the distribution of a proportionate number of band 6 marks. So, if achieving 90+% marks throughout the year feels impossible in some subjects, don’t feel as though this is a direct reflection of how your marks will look in the HSC and what your final mark will be.

To achieve the best marks possible in your courses, we recommend checking out the KIS Academics HSC Course page for some resources to help you!

How does the ATAR work?

By now you should understand how internal and HSC marks are both scaled using NESA’s statistical methods. After these marks are calculated, a final mark for each subject is awarded. A score out of 50 is assigned per ‘unit’, hence each 2-unit subject provides a mark out of 100 and each extension (or one unit) subject provides a mark out of 50.

Your 10 best units are selected to contribute to your ATAR, including 2 English units, and cumulated. Then, all scores (which will be out of a total of 500) of everyone who started year 7 in the same year in the whole state, are ranked.

An ATAR of 80 means your final score out of 500 is equivalent to or higher than 80% of the rest of the state. This is due to the application of a percentile algorithm.

The ATAR includes all students who began year 7 in the same year as you, including those who dropped out during high school or didn’t sit in the HSC. This causes the average ATAR to sit higher than the average percentile of 50 and is more like 70.

Key points:

·      Your HSC mark is YOUR HSC mark. Aside from the scaling factors between different subjects, this is not adjusted based on the performance of your school’s cohort.

·      Don’t focus too highly on the raw internal marks throughout the year. These numbers are scrapped and your internal assessment scores are determined based on your school’s final HSC exam performance (according to individual assessment rankings). Instead, focus on improving your rank as much as possible in every subject. Remember, English is compulsory in contribution to your ATAR.

·      Following the previous point, it’s important to work with others (not against them), especially after trials as you are no longer competing within your school’s cohort for the highest rank! As you will now understand, it is beneficial for your whole cohort for your school’s group to do as well as they can to benefit everyone’s individual marks in the scaling process. The better everyone performs in the final HSC exam, the better your moderated internal marks will be!

·      In terms of subject scaling, it can be tempting to choose the best scaling subjects in an attempt to maximise your marks for the best ATAR. Whilst there is some truth in this, do not choose subjects you have no interest in or that your performance is struggling too majorly. At the end of the day, your marks will reflect your own performance (and those of your school), so it’s still important to choose subjects you enjoy and excel at! It can be beneficial to assess previous years’ scaling reports to assess previous subject patterns and make the best decision for you.

·      Whilst some ATAR calculator predictions can be somewhat accurate using current marks, many of them provide wildly inaccurate estimations if they don’t consider factors such as your school’s scaling or rankings!

Frequently Asked Questions (FAQ Section)

Are raw internal marks really important?

Don’t focus too highly on the raw internal marks throughout the year. These numbers are scrapped and your internal assessment scores are determined based on your school’s final HSC exam performance (according to individual assessment rankings). Instead, focus on improving your rank as much as possible in every subject. Remember, English is compulsory in contribution to your ATAR.

What is the purpose of scaling?

Subject scaling is necessary to reflect the relative difficulty of the exams and the capability of student cohorts across different subjects. The easiest comparison to make is between Standard English and Advanced English.

What happens to your best 10 units in HSC?

Your 10 best units are selected to contribute to your ATAR, including 2 English units, and cumulated. Then, all scores (which will be out of a total of 500) of everyone who started year 7 in the same year in the whole state, are ranked.


This article is written by KIS Academics tutor, Abby Hughes. Studying the Bachelor of Veterinary Biology/Doctorate of Veterinary Medicine at the University of Sydney, Abby has tutored several students in a variety of subjects and is passionate about maximising student potential. You can review Abby’s profile on the website and request her as a tutor.

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