How the HSC works: Understanding New South Wales' Year 12 ATAR System

Let’s break down the HSC and what it entails, so you (whether you are a student, parent, or tutor) are ready for the rollercoaster ride that is Year 12.

2 years ago   •   5 min read

By KIS Academics
Photo by April Pethybridge / Unsplash

🌃 The Higher School Certificate (HSC): What is it?

Exactly how the mythical HSC works is a constant source of confusion for parents and students - sometimes even for those currently undertaking HSC subjects. Hopefully all of the following information - is explained to you by an HSC survivor! - will clarify the key points of confusion. Here's a quick guide, if you need to brush up on how the ATAR works. If you're still on the fence when choosing the right HSC subject, it might be helpful to check out our comprehensive HSC Subject Selection Guide.


State: NSW

Governing Body: NESA (NSW Education Standards Authority)


The HSC works on a “units” system. Most classes are two units (English, Math, Chemistry etc), but extension subjects are only one unit (English Extension, Math Extension etc). If you're still unsure what the difference is between each maths subject, here is a quick comprehensive guide.

In year 11 you are required to take a minimum of 12 units (for most people this is 6 subjects).

In year 12 you are only required to take 10 units. Regardless of how many units you take, only the 10 best units will count towards your ATAR. Each unit is worth 50 marks and therefore for the standard 2-unit course you will receive a mark out of 100.

For Example:

My HSC Subjects

Often people stick with their 12 units from year 11 so that if they have a bad day, or mess up majorly on an exam, they have a fallback and it won’t drastically change their ATAR.

Extension Subjects:

As I mentioned, extension subjects are one unit. This is because they are half the amount of class time and a shorter exam (only 50 marks). However, as you can see in the example above you still do the advanced course as well. So, in total, you end up taking 3 units of English if you want to do the extension course.

Extension 2 courses are only offered in year 12 and only for English and Maths. You must be enrolled in Extension 1 to be able to do Extension 2, so this takes your total up to 4 units of English or math respectively. Math, as you can imagine, is a very challenging course that is harder than advanced or Extension 1. However, with English, Extension 2 is a “Major Work”. I will go into more detail about this in the subject section.

If you're interested in a more in-depth explanation of the difference between the HSC maths subjects, here is a comprehensive guide!

Internal and External Assessment:

For every course, regardless of the units, your final grade is made up of:

  • 50% internal marks
  • 50% of the external exam

Except it’s slightly more complicated than that. Your internal marks are never entered into NESA. What gets entered is your rank within your cohort at your school. I think the easiest way to explain this is with an example.

Example: Ally, Bella and Cassie go to School X, and they all take English Advanced. Below are their marks and ranks in that course:

Most importantly: no one can take your External mark away from you. What you do on the day is yours and you keep it.

But each school’s assessments have a different level of difficulty, so it wouldn’t be fair if a school made their assessments super easy and everyone got 100%.

What ends up happening is your “Raw Mark” gives you a rank in your cohort and then what NESA records for the internal assessment is the corresponding mark that someone from your school got in the external (eg. If you came first in internals, your internal mark would be recorded as the top mark someone at your school got in the external).

So, looking at Ally, Bella and Cassie again, their raw marks would turn into:

Ally came first in the internal so her internal mark is what the person who came first in the external exam got, Bella, came second so gets the second-best mark and so on. Remember: this is only for your internal 50%, you still keep your exam mark to make up the other 50%. So the girls would end up with these final marks for the course:

The upshot of all of this is: you want to beat everyone in internals and then help everyone for externals, so all your marks get bumped up.


Ok so now you have all your subjects, and you’ve got your final mark, but how do you get the magical ATAR?

First and foremost, 2 units of English count towards your ATAR. Regardless of how well or how bad, even if it’s your worst subject and you have done 12 units … it’s going to count. But these are your 2 best units of English, so if you do Extension 1 and mess up your advanced exam, extension 1 will count and half your advanced will count.

If we take this made-up student as an example:

At face value, it looks like chemistry isn’t going to count. But this is where scaling comes in. Chemistry is a harder course, so it’s known to be ‘high scaling’, meaning if you do well in it, it will boost your ATAR. Legal Studies is an easier course so even though they did well chemistry might count instead.

I could explain how this works but honestly, it’s not important. Once your marks are in it’s out of your hands. The advice I always received is to choose subjects you are good at and interested in and the rest will take care of themselves. Don’t choose a subject simply because it will boost your ATAR, if you don’t do well in it, it doesn’t matter how well it scales.

In Conclusion...

The HSC system can be quite complex, and understanding what's going on can be very daunting for new students and parents. If you ever need some assistance with HSC studies or subject-specific help, KIS Academics tutors have a thorough understanding of their subjects and can assist in understanding curriculum requirements. Our private tutors are able to provide materials and teaching on how to prepare for HSC internal and external assessments. Learn about our HSC tutoring and book a free study skills consultation with a KIS Academics tutor.

Written by KIS Academics Tutor and State Consultant for New South Wales (HSC), Emma Ashley. You can view Emma's profile here and request her as a tutor.

Disclaimer: KIS Academics is not affiliated with the New South Wales Education Standards Authority (NESA). For a more detailed overview of the HSC, please refer to NESA materials.

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