Published by the Institute for the Study of Labor in Bonn, Germany, the study's findings are based on a statistical analysis of the results from the 2009 Programme for International Student Assessment (PISA) for reading, maths and science in each school sector. It controlled for a number of student and school characteristics apart from SES, including Indigenous background, location, school type, time spent on subjects, student/teacher ratio, shortage of qualified teachers, computers per student and absenteeism. The study also showed that a small part, roughly 6-7 per cent, of the total variation in test scores is attributable to unobserved factors after controlling for student and observed school effects. This residual effect is interpreted as a measure of school quality including influences such as the learning environment of the school, ability of teachers, leadership, etc. This finding suggests that the part of school quality that is hard to quantify and measure in the data, "has much less of an independent effect on student outcomes than we may sometimes be asked to believe" The study also tested whether this residual measure of "school quality" was significantly smaller or larger for government schools compared with private schools. It found no significant difference for reading, maths or science. This is a simple but powerful result, which suggests that when we compare the quality distributions between Government and non-Government schools, we cannot find any statistically significant difference.

Similar tests were conducted comparing the estimated quality of government, Catholic and Independent schools separately. In the case of reading and science, the estimated school quality does not differ significantly between school sectors. In the case of maths, government schools performed better than Independent schools while Catholic schools performed slightly better than government and Independent schools. However, the study warns that these results should be treated with caution because of the small sample sizes when private schools were split into Catholic and Independent schools. The findings of the study are consistent with those of several studies in the past year or so showing that private schools do no better than public schools. The results from the OECD's Programme for International Student Assessment (PISA) in 2012 show no statistically significant difference in the results of public, Catholic and Independent school results after taking account of the socio-economic background of students and schools. The report said that: "students in the Catholic or independent school sectors bring with them an advantage from their socioeconomic background that is not as strongly characteristic of students in the government school sector". A study published in the Economics of Education Review last December by economists from La Trobe and Monash universities shows Catholic schools' performance has declined since 1980 relative to government schools. It says that the advantage that Catholic schools once held over government schools has virtually disappeared and attendance at Catholic schools may now lead to lower completion rates in secondary school and university. It noted Catholic schools' falling performance from 1980–2000 coincided with a large increase in funding. This raises questions, it says, about how well these increased resources have been used. Another study published in the same journal by an economist at the Melbourne Institute for Applied Economic and Social Research shows that the decline in Australia's performance in international tests over the decade is primarily due to falling results in private schools, the falls being similar in both Independent and Catholic schools. At the school level, the declines in performance of schools have not been associated with many of their observed characteristics, other than that the declines appear to have been concentrated among private schools. Where private schools once generated better outcomes than public schools, given the compositions of their student bodies, this was not the case after 2003. [p.237]

The study noted that the decline in performance in Independent and Catholic schools occurred despite substantial increases in government funding over the period. These funding increases greatly exceeded those for government schools whose results appear not to have fallen. This suggests that private schools have used their funding increases much more ineffectively than government schools, raising the question of what benefit the nation's taxpayers have received from this expenditure. The new study from the National Institute for Labour Studies concludes that there is no evidence that private schools are any more efficient in utilising resources than public schools: "This paper does not find any evidence that non-Government schools show any capacity to utilise the funds at their disposal more efficiently than their Government school counterparts.... .... Our paper provides evidence that even after we subject some of the best data available to probably the most sophisticated methodological testing available, we can still find no evidence that the non-Government sector puts funding to a more efficient use than the Government sector." It says that its findings provide support for a new funding model based on improving equity in education. This is exactly what the Gonski funding model is designed to do. It should be fully implemented nationally and not continue to be dismembered by the Federal Government. Trevor Cobbold is national convenor of Save our Schools.