About 80 percent of schoolgirls in Liberia's capital have to sell sex to pay for an education believed to be their only way to escape from poverty.
Save the Children's findings underlined the social crisis in the West African country, which is holding elections next month in an attempt to draw a line after 14 years of civil war that created a generation of orphans and tore the state apart.
"We surveyed more than 300 girls over a five-month period, and initially we were not aware of this issue," said Pippa Ranger, a spokeswoman for the London-based charity.
"Gradually the opinions we collected pointed to a figure of between 60-80 percent (of schoolgirls selling sex), showing that this is a widespread problem with implications far beyond education," she said.
According to the Save the Children fund study approximately 60 million girls round the world have no access to education due to poverty, conflict and discrimination, Reuters reports.