After paying for her uniform and textbooks, some days there is only enough for one meal of rice - some days not even that. Amid 85 per cent unemployment, Precious is working in an overcrowded market. She is in the ninth grade.

Save the Children believes between 60 and 80 per cent of Liberian girls sell sex to fund their education and basic living costs. The charity says men prefer younger girls - who are thought to be cheaper, more pliable and less of a health risk - than their older sisters.

Research released by the group on Monday shows it costs half the income of an average Liberian family to educate one child for a year.

Liberia is a failed state. The epicentre of West Africa's conflicts, it has had no electricity, running water or land lines for 14 years. It has been shattered by decades of corruption and years of civil war, when drugged-up child soldiers rampaged through the capital. Sometimes they ate the hearts of enemy dead. A quarter of a million died.

Two years after a peace deal was signed in 2003, the rebels have been disarmed and former president Charles Taylor is in exile, under indictment for war crimes by an international court. Liberia is patrolled by 15,000 heavily armed UN peacekeepers and ruled by a transitional government due to hold elections on October 11.

As the 22 presidential hopefuls campaign, it is promises of free education that draw the biggest roars from the crowds. For a generation of Liberians it is seen as the one sure-fire ticket out of the poverty trap.

When Liberian soccer hero George Weah began his campaign recently, he said: 'I want to send more teachers and students abroad to strengthen our educational system.' The next sentence drowned in cheers. The former Chelsea player's rags-to-riches story of growing up in the country's slums is a dream come true for girls like Precious.

'Sometimes I am afraid,' said 18-year-old Mary. 'I am afraid that [some] person will kill me. Sometimes they can beat me ... but I feel fine if I get money because I am saving for school.'

After her older brother was killed during the war, selling sex was the only way to survive. Mary refuses to have sex without a condom, although she would be paid twice as much. 'They ask but I say no,' she said. 'If I get pregnant, how will I go back to school?'

She is excited by the new-found peace that has come to her country and the opportunities it might bring.

At a donor conference last year, the world promised more than US$520 million to help rebuild the country - more than five times the annual budget. Concerns about corruption mean the aid is funnelled through non-governmental organisations rather than the government, resulting in projects like the local resource centre being run by Save the Children, where used textbooks line the walls for those who can't afford them.

'Many of these children have lost the true meaning of what society is. The thing that binds a family together has been broken by war,' said Helen Harris, a social worker at the centre. 'If a father goes out to work everyday and comes home with nothing, will his children respect him? They have to make their own way.'

The girls at the centre have simple dreams - to be a nurse, work in an office, sleep alone at night.