Pupils in the UK who attend private schools get a substantial educational head start over those who attend state sector schools, a new study has found.
Researchers from Durham University have found that private school pupils are up to two years ahead of their state sector counterparts and outperformed them in virtually every subject by an average two thirds of a grade in each subject at GCSE level.
The biggest differences in grades were in subjects like French, history and geography with the grades closer in scale in chemistry, biology and physics,
The study, commissioned by the Independent Schools Council (ISC), found pupils in the independent sector were ahead of all their peers at all ages, beginning at four.
Without taking into account background, private school pupils got GCSE results nearly two grades higher per subject, which means an A grade rather than a C. By including factors like academic potential, family wealth and gender, this fell to about 0.64 of a grade.
Professor Robert Coe, told The Times: "It is always difficult to unpick the causes of any differences, and we think it is unlikely to be purely an effect of better teaching in independent schools."
The study found that pupils from UK private schools would outperform those of high-achieving nations such as Finland, Switzerland, the Netherlands and be equal with South Korea and Japan.
While Julie Robinson, of the ISC, said it proved that independent schools are worth paying for, it will raise doubts over government claims that the gap between private and state schools is closing.
A recent study showed that private pupils were more than twice as likely to attend a Russell Group University and five times more likely to go to Oxford or Cambridge than state sector pupils.