However, the wage premium dropped sharply when the researchers isolated the effect on earnings of family background. The SMF looked at the earnings of people from the same sort of families that typically send children to private schools – better-off and better-educated, and with high ambitions for their children – but who attended state schools.

The earnings gap between those children and their privately educated peers was only £57,653 over 16 years.

The average annual pay gap between those educated at private schools and those from the state sector — £3,603 – is well below the average annual fee for private day schools of £12,153, or £27,600 for boarding places.

Emran Mian, the think tank’s director, said: “These huge differences arise in part because these children come from privileged backgrounds anyway. But that’s not the whole story. Take two people of the same ability at age 11 and with the same parental background, track them forward, and the pupil who attends independent school is likely to earn more.”

The Sutton Trust, an education charity which commissioned the research, wants the Government to reintroduce a form of the old Assisted Pl……………. continues on Telegraph.co.uk