Girls in the developing world are still missing out on school, says the Save the Children charity.
In South Asia, 40% of girls from poor families miss out on education
A report launched on International Women's Day said 60 million girls were not going to school - a higher proportion than boys, says the charity.
Save the Children wants the UK government to increase its overseas aid and to promote fairer educational chances for girls.
A lack of basic education is trapping girls in poverty, said the report.
Discrimination and family hardship could mean that girls were not able to go to primary school.
'Burden of poverty'
School fees, even when very low, could deter families from giving girls a basic education, which could consign them to a low-income, low-status life.
"The burden of poverty falls particularly heavily on girls. If parents can't afford to send all their children to school, it's the girls who usually lose out," said the report.
The gender gap in education was at its biggest in sub-Saharan Africa, said the report, with 23 million girls completely missing out on school. Only 5% of girls in some countries in this region went to secondary school.
In India and Pakistan, 22 million girls missed out on school. And 40% of girls from poor households in the region did not reach the end of their first year in primary school.