Eton School
Eton College , known for the Eton Wall Game, is one of the world's most famous independent schools Reuters

Private school children earn almost £194,000 more on average in the early stages of their careers, when compared to their peers from state schools, according to the thinktank the Social Market Foundation.

A report from the organisation calculated for the first time the 'wage premium' experienced by those attending independent schools.

The study found that between the ages of 26 and 42 someone who attends an independent school will earn a total of £193,700 ($332,185, €243,440) more than someone who attends a state school.

Even when factors, such as family background and early educational achievement, are accounted for, the wage premium persists at £57,653, according to the research.

The Social Market Found explained that the better educational achievement of those attending independent schools is a major contributor to the wage difference.

"The evidence is overwhelming that independent schools confer a massive advantage on their pupils," said Dominic Raab, a Conservative MP.

"Rather than knocking independent schools down, we should be opening them up on a meritocratic basis.

"If we're serious about establishing ladders of opportunity for the bright kid from the council estate or rural backwater, this is the way to do it."

The report also assessed The Sutton Trust's Open Access scheme, which seeks to open independent schools up to pupils from all backgrounds based on academic ability.

The proposal is that participating schools receive the same funding per pupil as local state-funded schools currently get, but also charge fees on a means-tested basis, with the poorest families paying no fees.

Using the latest data on independent school fees, the Social Market Foundation estimated that applying the scheme across 100 leading independent schools, covering 62,000 pupils, would cost the government around £215m per year.

"Forty years ago, most of the best independent day schools in this country were open to children of all backgrounds," said Sir Peter Lampl, chair of The Sutton Trust.

"Today, unless your parents can find £12,500 a year after tax, access is by and large denied."

"The stark truth is that an independent day school student is 55 times more likely to win an Oxbridge place and 22 times more likely to go to a top-ranked university than a state school student from a poor household. This is a shocking waste of potential."