The proportion of students doing high-level maths and science subjects in the HSC has steadily declined over the past 10 years along with Australia's performance in international tests, which experts say is linked to the country's attitudes towards STEM.
Only 4.18 per cent of HSC students did Maths Extension 2, the highest level maths subject available, last year. This was down from 4.58 per cent of the cohort in 2007.
Only 11.54 per cent of year 12 students did Maths Extension 1 in 2017, down from 13.18 per cent in 2007, and 22.36 per cent studied Mathematics, down from 26.99 per cent.
Maths General 2, which is a non-calculus course, remains the most popular maths elective, with 41.29 per cent of HSC students taking it last year. However, this also represents a decline from 44.27 per cent in 2007.
The proportion of students studying physics, chemistry, engineering and technology subjects has also seen a similar decline.
There was also a fall in the proportion of HSC students studying the top-level English Extension 2 course from 3.8 per cent in 2007 to 2.16 per cent last year.
However, the percentage of students taking the popular PDHPE course has increased from 18.64 per cent of the HSC cohort in 2007 to 20.43 per cent in 2017. The candidature for Modern History has also increased from 14.02 per cent of students in 2007 to 14.54 per cent last year.
Despite these figures, NSW Education Minister Rob Stokes said that the national promotion of STEM subjects over humanities subjects was an act of "intellectual snobbery", which has drawn comment from the country's top scientists and industry experts.
The Australian Mathematical Sciences Institute (AMSI) school program manager Janine McIntosh said that general attitudes towards maths and science are a big part of the problem.
(ACER), said the effect of the decline is visible in students' results in international tests such as the Programme for International Student Assessment (PISA) and the Trends in International Mathematics and Science Study (TIMMS).
"What we've found is that over the past 15 to 20 years, we have fewer students performing at the advanced level," Dr Thomson said.
"We're average on the OECD scale for maths but certainly, our scores have gone down over the past 10 to 20 years.
"And in the questions where we ask students whether they like maths or science, only half say yes in year 4. By year 8, it's down to under a quarter and it's even lower at the senior levels."
Dr Thomson said a shortage of STEM-qualified teachers in high schools and anxiety about teaching maths and science subjects among primary school teachers is one reason for the fall in enrolments in high-level maths and science subjects and the country's overall declining performance.
"The other reason is that kids only choose subjects they know they'll be successful in," Dr Thomson said.
"If they know they'll only be moderately successful in advanced maths, they'll do general maths instead. And often they're advised to do that by their schools to maximise their ATARs."
The ATAR scaling system has advantaged students choosing Maths General 2 course with up to 6.5 marks more than those studying the Mathematics course, a report by the NSW Department of Education's Centre for Education Statistics and Evaluation (CESE) revealed last year.
However, new maths syllabuses that will be rolled out this year and next year will aim to address the problem by introducing common content and marking scales.