Private, Catholic schools do add value to students' results

Over the last few years several studies have concluded there are no differences in academic outcomes for students from government, independent or Catholic schools once statistical adjustments are made for students' socioeconomic status and other factors.

Studies based the on 2009 and 2012 Australian component of the (PISA) international student tests found the large differences in student performance between school sectors were reduced when students' socioeconomic background was taken into account. The differences disappeared when the schools' average socioeconomic status was taken into account.

A recent study on Year 5 performance in the National Assessments of Performance — Literacy and Numeracy (NAPLAN) found the higher scores of students from Catholic and independent schools disappear with a comprehensive set of controls, which includes prior achievement (such as Year 3 NAPLAN performance). Other statistical approaches led to the same conclusion.

The authors attribute much of the differences between school sectors in NAPLAN to “previous cognitive attainments” or natural ability rather than socioeconomic status.

Previous studies on school sector differences

Despite these studies, it would be wrong to conclude there are no school sector differences in student performance in Australia. School sector differences are well established for students' Australian Tertiary Admission Ranks (ATARs).

This conclusion is based on a number of studies of cohorts participating in the Longitudinal Surveys of Australian Youth study (between 1998 and 2009) and a study of 2010 school leavers in New South Wales.

Generally, the unadjusted gap (not taking into account other influences on student performance) in tertiary entrance rank between Catholic and government school students is about five ATAR points and the gap between independent and government school students is around 11 ATAR points.

When controlling for students' socioeconomic status, the Catholic-government school sector gap declines marginally, whereas the independent-government school sector gap declines by about one-third from about 11 to seven ATAR points.

School sector differences decline much more substantially when taking into account students' prior achievement. On average, when taking into account socioeconomic status and prior achievement, the Catholic-government school sector gap is three to six ATAR points and the independent-government school sector gap six to eight points.

New study confirms sector differences

I recently undertook the most comprehensive study of school sector differences to date. This study is more robust than previous studies based on survey data, since the data is both 100% accurate and complete. I analysed NAPLAN and tertiary entrance performance data obtained from administrative sources for all students (over 40,000) attending all Victorian schools who obtained an ATAR in 2011.

For ATAR, Catholic school students scored, on average, nine ATAR points higher than government school students. Independent school students scored 17 ATAR points higher.

The increments associated with the Catholic and independent school sectors were reduced to six and eight ranks, controlling for socioeconomic status, prior achievement (Year 9 NAPLAN performance), gender and language background.