‘Attending an independent school in England is associated with the equivalent of two additional years of schooling by the age of 16, new research reveals,’ says the Independent Schools Council in its press release about the findings of research it commissioned from the University of Durham.
The researchers warn their estimations could be affected by factors not taken into account during their analysis. This increased the possibility of overstating the effects of private schooling:
'It is possible that this is an overestimate of any genuine causal effect of attending an Independent school because of unobserved factors that would have affected the estimate.'
'...the jury is still out with regard to the true extent to which attendance at independent schools in England enhance the academic achievements of students when student and school-level differences are accounted for.'
The report was based on both number crunching and trawling the existing literature assessing the difference in outcomes of privately educated and state educated pupils. But there was one notable omission from the latter: OECD analysis following the 2009 PISA tests. The OECD found that when socio-economic background was factored in, UK public (ie state) schools outperformed UK private schools by 20 score points on the reading scale. This is way above the OECD average of 7 score points in favour of public schools.
If, as this report appears to indicate (caveats notwithstanding) that pupils from independent schools outperform state educated pupils by two years, then it should be expected this advantage would carry forward to university. But when privately educated pupils graduate they're outperformed by their similarly qualified peers from state schools. Research by the University of Cambridge found students from different UK educational backgrounds do equally well at Cambridge. And Oxford researchers came to the same conclusion: '...those who do get in [to Oxford], private school students perform about as well as state school students.'
The Oxford researchers raised the question about whether those state pupils who did NOT gain a place at Oxford would have achieved the same degree as those private pupils who DID get in. They concluded the more likelihood of private school pupils actually gaining a place was 'short-term teaching effects upon the secondary school grades of private school students'.
If the higher grades earned by private school pupils at secondary level were described by Oxford researchers as ‘short term’ and not lasting then parents who send their children to private schools might be asking if the considerable expense is worth it.
UPDATE 28 February 2016. I left two comments (posting as ex-secondary modern teacher) on the HMC website pointing out that (a) the Durham report did not prove 'beyond reasonable doubt that independent schools add significant value to children’s education' because it said 'the jury is out', and (b) the OECD found UK state schools outperformed UK private schools on the reading scale when socio-economic background was factored in. I left the comments waiting moderation. I've just checked and neither of my comments have been published and the note about waiting for moderation has gone.