It shows the world is not on track to hit its 2015 target for making primary education universal 'by a wide margin.'
The United Nations education fund (UNESCO)'s report released yesterday said that while an extra 52 million children enrolled in primary school from 1999 to 2008, — the number of children out of school is falling too slowly, to 67 million in 2008.
"If current trends continue," the report warned, "there could be more children out of school in 2015 than there are today."
It highlighted the 'hidden crisis' of youngsters caught in armed conflict as one key reason.
“Armed conflict remains a major roadblock to human development in many parts of the world, yet its impact on education is widely neglected," said UNESCO'S Irina Bokova, at the report's launch in Dakar.
Some 42 per cent (about 28 million) of children missing primary school live in poor countries affected by conflict, the report said. "Children and schools today are on the front line of armed conflicts, with classrooms, teachers and pupils seen as legitimate targets," it said.
In Afghanistan, there were at least 613 attacks on schools in 2009, up from 347 in 2008, the report said. Rebel groups in Pakistan have targeted several girls' schools including one in which 95 girls were hurt, it said.
Children are also being used as soldiers in 24 countries including Congo, Chad, the Central African Republic, Myanmar and Sudan, it added.
UNESCO also flagged up reports from UN Secretary General Ban Ki-Moon that rape and sexual violence are used widely as a weapon of war in many countries including Afghanistan, Central African Republic, Chad, Congo and Sudan. "Many victims are young girls," the report said, pointing to Congo where one-third of rapes involve children and 13 per cent are against children under the age of 10.
"In the eastern part of the Democratic Republic of Congo probably about half of all primary school-aged children are out of school," report writer Kevin Watkins, told the BBC. He said the school attendance figures for Congolese girls were the lowest in sub-Saharan Africa.
The threat of sexual violence harms victims' learning potential and creates a climate of fear that keeps girls at home, he said.