Children educated privately are three times more likely than state pupils to attain top A-Level grades, new government data has revealed.
Fresh figures are to reveal that those educated independently are more than three times more likely to achieve AAB in subjects identified by the Russell Group as "facilitating" entry to their universities, with 7% of state school students achieving AAB across the 2010-11 year group, compared with almost a quarter (23.1%) in the independent sector.
Nick Clegg is to spell out the "corrosive" impact that the rift in Britain's education system has on society in a speech on Tuesday.
His commitment to "narrowing the gap" across the country's schools marks the first update since launching "Opening Doors, Breaking Barriers: A Strategy for Social Mobility" last year.
The deputy Prime Minister will outline a set of indicators to measure the impact of government policies on social mobility, including those measuring the A-Level attainment gap between independent and state schools.
Mr Clegg will emphasise that social mobility is the "impulse" that lies behind the government's education reforms, including the pupil premium.
He will say at the conference, to be hosted by the Sutton Trust: "Education is critical to our hopes of a fairer society. Right now there is a great rift in our education system between our best schools, most of which are private, and the schools ordinary families rely on. That is corrosive for our society and damaging to our economy.
"I don't for a moment denigrate the decision of any parent to do their best for their child, and to choose the best school for them. Indeed, that aspiration on behalf of children is one of the most precious ingredients of parenthood.
He will add: "But we do need to ensure that our school system as a whole promotes fairness and mobility, that heals the rift in opportunities.
"We are committed to narrowing the gap in our school system - state and private - and ensuring that all children are given the chance to rise. The way to do that is to make the state education system better - to level up - and ensure that anyone can get ahead."
He is expected to reaffirm the Coalition's drive on reforming the pre-16 curriculum, plus improve teacher and school quality.