Privately educated children are likely to earn almost £200,000 more during their careers than those who went to state school, according to research.
A new study suggests that a significant "wage premium" exists for those who go to fee-paying schools.
This may be down to the fact that privately educated children are more likely to get good exam results and to go to a top university, it argues.
The study, by the Social Market Foundation, is based on an analysis of the Sutton Trust charity's proposal to open up access to independent schools by ensuring pupils are admitted based on academic ability, rather than capacity to pay the fees.
The findings, which also draw on existing data, show that between the ages of 26 and 42, a pupil who attended a fee-paying school will earn around £193,700 more on average that someone who was educated in the state sector.
It goes on to say that a former private school pupil earns, on average, around 43% more per hour at the age of 34, around 35% more at age 38 and 34% more at the age of 42.
The study suggests that even when a child's parental background and their test scores at age 10 are taken into account, there is still a "substantial earnings premium", with a private school pupil earning an estimated £57,653 more between the ages of 26 and 42 than a similar child who went to a state school.
The researchers conclude that there a range of factors may have an impact on earnings, but that better educational achievement plays a major contribution.
"Those who go to independent schools are more likely to get good A-levels, more likely to get degrees and to get them from the most selective universities," the study says.
"Not only are their educational outcomes better, but, on the best available evidence - value-added scores - independent schools (on average) progress their children more during their school years than state schools."
The Sutton Trust's proposal for an open access scheme would see participating private schools receive the same funding per pupil as local state schools, but also able to charge fees on a means-tested basis, with the poorest families paying nothing.
Extending the scheme to 100 leading independent schools, covering 62,500 pupils, would cost the Government around £215 million per year, the study estimates.
It suggests that if this scheme was introduced, with pupils selected on merit rather than ability to pay, the social make-up of these private schools would radically change.
The number of children coming from the top 10% of household incomes would roughly halve, the study says, while the proportion of children coming from the bottom 40% would more than double.
In a foreword to the report, Sutton Trust chairman Sir Peter Lampl said that the "stark truth" is that a day pupil at a private school is 55 times more likely to win a place at Oxford or Cambridge and 22 times more likely to go to a top-ranked university than a state educated child.
"This is a shocking waste of potential," he said.
Sir Peter said: "This report clearly sets out the advantages that can be gained from a good private education. We need to open those opportunities to more young people, transforming the independent sector to ensure that successful day schools recruit once again on merit rather than money.
"Forty years ago, most of the best independent day schools in this country were open to children of all backgrounds. Today, unless your parents can find £12,500 a year after tax, access is by and large denied."
A Department for Education spokesman said: "Our reforms are closing the gap between the rich and poor and allowing thousands more children to go to good state schools.
"We are raising ambition for all children through our new rigorous curriculum and qualifications and spending £2.5 billion to support disadvantaged children through the pupil premium. We are also setting up free schools so that more children have access to the kind of education previously reserved for the rich.
"These reforms are working. There are now a quarter of a million fewer pupils in failing secondary schools than there were in 2010, and more young people from disadvantaged areas in England are applying to university than ever before."