A new study from the Sutton Trust has found that poorer students are considerably less likely to study the A-levels that are required to help them into leading universities.
Miliband is confident that his promise to invest more better reflects the public's priorities. But the Tories will present him as profligate.
Miliband revives 1997 pledge to limit class sizes to 30 pupils for 5 to 7-year-olds.
According to the research by the Sutton Trust, 31 per cent of parliamentary candidates attended private school, compared with 7 per cent of the population.
Both parties are grappling with their approaches to education as the election campaign heats up.
It is a fallacy that attention to the private-school question will distract from improving state education. For 70 years this has been a tired excuse to avoid a difficult problem.
Private schools instil their children with a sense of entitlement and confidence that is lacking among state-school pupils, argues Rhiannon Lucy Cosslett.
Running schools as charities has simply insulated them from the consequences of their own financial incontinence.
Private schools allow the privileged to buy their way into every structure of power in this country with barely a whisper from the rest of us. Why give them tax relief as charities when so many do next to nothing to earn it?
Shadow education secretary Tristram Hunt warns private schools: "The time you could expect something for nothing is over".