Australia's "misplaced reliance" on parental choice and competition between public and private schools may have created the conditions for declining student performance, warns a new paper investigating the "unsolved mystery" of worsening test scores.

The paper looks at Australia's "significant decline" in the OECD's Programme for International Student Assessment (PISA) results between 2000 and 2015, but focuses on mathematics because maths scores have dropped more than reading or science.

Australia has seen a sustained decline in PISA scores, especially in maths. Credit:Cathryn Tremain

As well as an emphasis on school choice, the quality of teaching in Catholic schools – which has shown the greatest decline in maths scores – could be another reason for worsening PISA results, the paper says, along with different education policies and practices in NSW and Victoria.

The paper says that expert explanations have failed to answer the riddle of why Australia, along with countries such as the Netherlands, Finland and Canada, have sustained decreases in PISA scores and says despite much "handwringing" from policymakers, there is no strong empirical evidence behind the PISA results.