HSC Extension Subjects
What is the opportunity presented to high achieving students?
Extension subjects present an excellent opportunity for students to do more of what they’re best at and at a higher level. There aren’t a lot of extension subjects in the HSC, and the ones we have are varied in the opportunities they present high achievers to have it count positively to a very high ATAR.
Below are some of my thoughts and charts on extension subjects in the HSC. I haven’t included languages. There are just too many of them with few students. Perhaps in another post.
Jump to a subject:
Achievement within extension subjects is peculiar just to them. Although they share the same band scale, how that scale is interpreted is unique for each subject.
English
Extension English subjects are, in my opinion, under studied. Changes to the format of future external assessments in Extension 1 and especially in 2, seem unlikely to nudge candidatures in a positive direction.
In 2025, 3,691 students completed English Extension 1 and 1,423 students Extension 2. English Extension provides students with ample opportunity for high contributions to high ATARs. Extension 1, in particular though, does have some quirks.
English Extension 1
The proportion of students studying English Extension 1 has significantly decreased since 2007. In 2007, 9.5% of HSC students studied Extension 1. In 2025 it was 4.6%. Over the same time the proportion of students achieving at E3 and E4 level has risen, particularly E4s, almost doubling.
The proportions of students achieving different ATAR levels hasn’t changed very much over that time.
When there’s an increase in the proportion of students achieving in the top band, but not much change in the ATAR contributions being achieved by the cohort, the natural consequence will be a diminishing of the value of those lower E4 scores to student ATARs, and that’s exactly what we’ve seen in Extension 1 in recent years.
Here is how English subjects, by my estimates, scaled in the 2025 HSC.
Each dot is an HSC score, coloured by band. How far across they are to the right is what those scores are worth as individual contributions to ATAR scores. So the pink dots on the right are Band 6 scores and the left most pink dot is an HSC score of 90. So an HSC score of 90 in English Advanced was worth an ATAR contribution of about 96.
An HSC score of 45, the lowest E4, in Extension 1, though, was worth about 93 as an ATAR contribution. There’s something backwards about this. I think it would be reasonable to assume that the academic standard to reach the highest band in English Extension 1 would be higher than the standard to reach a Band 6 in English Advanced. But it’s not. There’s not a heap in it, but in recent years the gap between a 45 in Extension 1 and a 90 in Advanced (and Standard) has been widening, with the 45 in Extension 1 moving backwards.
Here’s what Extension 1 bands were worth as contributions to ATARs in 2025.
The higher E4 scores in Extension 1 are worth heaps to student ATARs and there’s plenty of opportunity for high contributions to very high ATARs.
Here’s the distribution of HSC scores in English Extension 1 in 2025.
There were over 300 students who achieved an HSC score of 48+ and those scores are worth 99.5 and more to student ATARs. About 42% of students achieved an E4 and the most common of those scores was 45. Achievement is really concentrated at that high end.
In terms of opportunities for ATAR contributions, there’s a lot to like.
Nearly 20% of the cohort achieved contributions to ATARs of 98 or more, although the majority of those were from 98-99. There are still a lot of scores at 99+.
English Extension 1 can get you there, but students do need a solid E4 score for it to be a positive contributor to a very high ATAR.
English Extension 2
Like Extension 1, English Extension 2 has seen a decline in rates of participation. With 3.8% of NSW HSC students studying Extension 2 in 2007, dropping to 1.8% by 2025, participation is about half of what it was. It’s also seen some pretty significant change in E3 and E4 achievement, dropping to 2018, then rising again until now. In 2025, about 89% of students achieved an E3 or E4 in Extension 2.
There hasn’t been as much change in the overall ATAR achievement of the cohorts in Extension 2 as there has been in band achievement. The result of this is that what HSC scores are worth to ATARs changes, rather than the ATAR achievement of the cohort itself.
Extension 2 contributions to ATARs aren’t drastically dissimilar to Extension 1. There is a lower proportion of students in Extension 2 achieving E4 scores, but they are also worth slightly more as contributions to ATARs, so that makes sense.
Like Extension 1, Extension 2 scores peak at low E4, but the slope up is less steep. I think it’s just that there’s a higher proportion of students hitting the middle E3 scores in Extension 2 than in Extension 1.
Opportunities for higher contributions aren’t quite a plentiful in Extension 2, but they are there.
In Extension 1, nearly 20% of students achieved contributions of 98+, but in Extension 2 it’s only just over 10%. I think this is just because it’s not the top Extension 1 students taking Extension 2. It’s more representative than that.
Extension 2 is an odd subject. Following excellent advice is essential. There is some subjectiveness to how it’s marked. This is true in every subject, but because it’s the marking of a single project, there’s less smoothing out the effects of that.
It’s a unique opportunity for students to complete a big project with a wide scope of what they do. English Extension 2’s future feels uncertain to me. I hope the addition of the exam doesn’t have too much negative impact on the course.
Mathematics
Maths Extension 1 and 2 are the most popular extension subjects. With 9,279 and 3,844 students respectively, they’re popular options for high achieving HSC students.
Because of their enduring reputation and, for whatever reason, their ability to instill fear in the hearts of students who aren’t ready to study them, Maths Extension 1 and 2 tend to have, proportionally, fewer lower achievers across the state than other subject. The median contribution to ATARs is well above other subjects, with only Latin Extension in between the two, but with only 80 students in the state last year, it’s statistics are somewhat skewed.
Mathematics Extension 1
Unlike English Extension, Maths Extension 1 cohort sizes have remained relatively steady. There’s been a small drop from 2007 to 2025, but nowhere near as much as some other traditionally higher achieving subjects. Band achievement has also remained relatively consistent. Maths Extension 1 is a subject without too much change.
E4 scores in Maths Extension 1 are worth an awful lot to ATARs.
An HSC score of 45 or 90, depending on whether it’s worth one unit or two, is worth, by my estimates, about 98.5 as an ATAR contribution.
With 3,222 of the 9,279 students achieving an E4, that’s a lot of very high contributions to ATARs. Maths Extension 1 gives a rare insight into how students at the next level achieve compared to those who don’t. A student in Maths Extension 1 can only achieve an odd score if they’re also studying Extension 2, so we can see the distribution of the scores Ext 2 students are achieving in this chart.
Maths Extension 1 has a high proportion of contributions to very high ATARs. In 2025, by my estimates, 3,353 Maths Extension 1 students achieved an ATAR contribution of 98+ from their Maths result.
Most of the highest ATAR achievers in NSW have Maths Extension 1 as part of their pattern of study.
Mathematics Extension 2
Like Maths Extension 1, Extension 2 has remained relatively steady. With a persistent candidature of 4.5-5% of the state, there’s not much that changes about the Extension 2 candidature and their achievement in recent years.
Maths Extension 2 has the highest scaling top band in the HSC. Any E4, by my estimates, was worth over 99.4 as a contribution to a student’s ATAR in 2025. That’s a lot. Anecdotally, Maths Extension 2 is the most likely subject in the HSC to be a positive contributor to a student’s ATAR. In the schools I work with, Extension 2 is a positive contributor to student ATARs over 90% of the time. I do know that in my estimates I overestimate the value of HSC scores of the bottom 25% of the state cohort more than other subjects. Above that, I’m confident my estimates are quite close.
Of the 3,844 students who studied Extension 2 in 2025, 1,595 of them achieved an E4 score. That’s a lot of high contributions to very high ATARs.
There’s not too much to say about all this. The opportunities for high contributions to high ATARs in Maths Extension 2 are unparalleled. If a student is capable of and interested in Maths Extension 2, it’s a subject which, though a lot of work, pays off for ATARs, when that matters for students. It also makes you a smarter mathematician.
Science Extension
Science Extension is a small subject. About 1% of students study it and for the seven years it’s run, this has remained pretty steady with a little growth.
Of all extension subjects, Science Extension has the lowest proportion of E4 scores. It’s important for schools to know this. If they’re seeing higher proportions of top band scores achieved across other extension subjects, that doesn’t necessarily mean there’s a deficit in achievement for Science Extension. It may simply be that the cohort at the school is somewhat representative of the state.
One thing I feel should probably be a goal at band allocation time is that the proportion of students achieving bands is relatively appropriate to the population studying that subject. That is, I think it should be academically easier for students in Industrial Technology to achieve Band 6 scores than it is for Chemistry students. And it is. But Science Extension is a subject where this doesn’t really happen.
Here’s how Science subjects scaled in 2025.
I wouldn’t be surprised if the goal for Science Extension E4s is that their difficulty to attain be on par with a Chemistry Band 6. I think, overall, this is probably a good goal. The only problem is I think Chemistry Band 6 scores are too difficult to achieve. It’s not a big deal when we have the context, but an E4 in Science Extension is more difficult to achieve than an E4 in other extension subjects, except Maths.
E3 scores, on the other hand, are broad in their ATAR contributions, with 69% of the cohort achieveing an E3. That’s a lot of E3s.
In 2025, there weren’t a lot of high E4 scores. Right now, Science Extension isn’t attracting the highest achieving science students in the state. I think that’s a shame, as it seems to me to be a pretty great subject. But it’s how it is right now. Because the numbers are quite small, it wouldn’t take too many students to change that and improve the ATAR contribution opportunities available at the top end of the mark range.
At the top end of ATAR contributions, there weren’t heaps of opportunities for Science Extension students in 2025. For an extension subject, I wish there were some more students hitting those very top marks.
Science Extension does offer opportunity for very high achievers to have Science Extension as a positive contributor to their ATARs, but not as many as some other extension subjects. I hope that will change over time.
History Extension
History Extension has experienced a decline in the proportion of students taking it on as a part of their pattern of study. E3 and E4 achievement has increased significantly since 2007, such that in 2025, nearly 90% of the cohort achieved an E3 or E4 band.
History Extension has experienced some change to its cohort over this time. The top 10% of the cohort are now slightly higher achieving than they were in 2005, although the median ATAR contribution has decreased quite a bit. That is, there is a higher proportion of higher achievers than in the past, and also a higher proportion of lower achievers. There’s less of a middle. It’s not a problem, it just is.
Anecdotally, I notice in schools that a number of students interested in taking on History Extension are not typical extension students and would probably not consider taking on extension English or Maths.
In 2025, by my estimates, an HSC score of 45 in History Extension was worth about 91.5 to a student’s ATAR. This may seem a little low for an extension subject. Except for Music Extension, an E4 in History Extension is worth less than an E4 in other extension subjects.
Here’s what scaling looked like in 2025 for all HSIE subjects.
An E4 in History Extension is, as a contribution to ATARs, similar to a Band 6 in Modern or Ancient History.
These are all scores achieved in History Extension in NSW in 2025. I wrote above that there was less of a middle than in the past. The middle is still substantial, though.
Because HSC achievement in History Extension just drops off at an HSC score of 48, it’s difficult to discern the HSC scores that are contributing to the highest ATARs, but they are there. About 4.6% of the cohort in 2025 achieved an ATAR contribution of at least 98 and a quarter achieved an ATAR contribution of 90+.
History Extension can get you there. The opportunities at the very top are not as plentiful as some other extension subjects, but the opportunities aren’t so lacking that higher achievers should shy away from it.
Music Extension
Music Extension is wild. No other subject in the HSC is like it. Candidature has remained pretty steady at just over 0.5% of students taking it and there have been some fluctuations in the band allocations. In 2025, about 98% of students in Music Extension achieved an E3 or E4. That’s a lot.
What bands are worth to ATARs in Music Extension does not look good. But this needs to be put into context and that context is that the most achieved scores in Music Extension are the highest scores and they scale very well.
Of the 447 students in Music 1 in 2025, 341 of them achieved an E4. 165 of them achieved 49 or 50 out of 50. So whilst a low E4 in Music Extension is not a high scaling score, if you achieve an HSC score of 45, you’re achieving in the bottom third of the state cohort.
The proportion of students in Music Extension achieving positive contributions to very high ATARs is much more encouraging than what it looks like the charts above this one are showing. Only Maths Extension 2 has a higher proportion of students achieving a 99.5+ ATAR.
Music Extension is, for the right students, at the right time, who put in the effort and follow good advice, an excellent opportunity for a high contribution to a very high ATAR.
