The widespread perception that private schools deliver better results than public schools has taken another blow. A new study of NAPLAN results shows that public schools do as well as private schools after differences in socio-economic background of students are considered. This is despite the large resource advantage of private schools.
The study found that, after taking account of the different socio-economic background of students in school sectors, private schools are not associated with higher average student achievement in standardized literacy and numeracy tests at any grade. Nor do private schools provide greater progress in reading and numeracy from grade 3 through grade 9. The study concludes:
The results support and extend on previous studies using largescale samples and similar methodology which indicate that school sector differences are largely explained by differences in the background characteristics of students who select into different school sectors. [p.22]
It said that the results raise serious questions about the worth of a private school education, especially one heavily subsidised by the taxpayer.
These results lend additional support to the argument that the high investment in private schooling in Australia does not necessarily lead to better achievement outcomes for students attending those schools. [p. 24]
In terms of equity, our results support analysis from the OECD in indicating that a large independent school sector, underpinned by market values of competition and choice, and supported by high levels of government funding are not optimal features of an equitable education system. [p. 28]
The study examined whether differences in literacy and numeracy achievement were related
to attendance at public or private schools in a sample of 2,762 Australian students in grades 3, 5, 7 and 9 who completed NAPLAN between 2008 and 2018. It examined whether school sector differences were evident in NAPLAN achievement both at points of time and whether there were differences over time in the progression of students from grade 3 to grade 9.
It found that private school students marginally outperformed their public school counterparts in grades 7 and 9 in the raw scores, but the small differences disappeared after socio-economic status and prior achievement were included as covariates. No advantage of attendance at private schools was evident in grades 3 and 5.
The longitudinal analysis compared growth trajectories of NAPLAN results for different groups of students: those remaining in the public sector from grades 3 through 9, compared with those who remain in the private sector across this period, or shift to the private sector as they commence secondary school. Despite the differences in student background, the study found that students in both school sectors had similar growth trajectories in reading and numeracy from grade 3 through 9.
As the study noted, this provides evidence that private schools do not add value relative to public schools. The higher achievement of students in private schools in raw scores is dependent on the characteristics of the students who select into the schools, rather than any advantageous feature of the school sector learning environment.
The study further notes that the results highlight old questions about the utility of persistently high levels of taxpayer funding of private schools in Australia.
If private schools do not “value add” in terms of improving achievement in basic skills testing and tend to increase segregation based on student background and family socioeconomic status, some serious policy questions need to be asked about school funding structures…. [p.28]
Apart from these findings, the study also concluded that prior achievement is by far the largest predictor of student results in public and private schools, even more than socio-economic background. Inclusion of prior achievement in NAPLAN is intended as a measure of student ability. However, as a recent study has shown, this approach to analysing student and school results is fundamentally flawed. Prior achievement of students is also affected by student and school background characteristics and other factors such as school resources, parental involvement, and teaching practices. Inclusion of prior achievement as a variable dilutes or removes the effects of such factors.
This is demonstrated clearly by comparing the results of two analyses conducted by the new study. The analysis discussed above shows a significant effect of student background on NAPLAN results. However, when prior achievement is included in the analysis, the influence of student background is much reduced.
Apart from this problem, the study adds weight to the large volume of evidence from overseas and Australian studies demonstrating that public schools do as well as, or better than private schools. For example, the OECD report on the 2018 PISA tests found that student achievement in public schools in OECD countries was higher than in private schools [p. 158]. The Australian PISA 2018 report found no difference in student results in reading and science between public, Catholic and Independent schools after taking account of differences in student and school socio-economic background [pp. 55, 198]. Public school students achieved higher results in mathematics than Catholic school students [p. 135].
Thus, public schools in Australia do as well as private schools despite having far fewer human and material resources than private schools and being disadvantaged by government funding policies that have heavily favoured private schools. It all suggests that private schools are less efficient than public schools in using their resources.