Over 300 million children globally between the age of five and 17 years of age were not in school, the Unicef said in a news report.
More than one-third of them, or about 104 million, are in countries affected by conflict or disaster, the report titled "A future stolen: young and out-of-school" revealed on Wednesday.
Additionally, it said one in five young people between 15-17 years old in countries affected by conflicts and disasters have never even entered any school and two in five have never completed primary school, reports Xinhua news agency.
"When a country is hit by conflict or disaster, its children and young people are victimized twice," said Henrietta Fore, Unicef Executive Director.
"In the near term, their schools are damaged, destroyed, occupied by military forces or even deliberately attacked, and they join the millions of young people out of school, and as the years progress they seldom return.
"In the long term they -- and the countries they live in -- will continue to face perpetuating cycles of poverty," she said.
By current trends, the number of 10 to 19 year-olds will rise to more than 1.3 billion by 2030, an increase of 8 per cent, the report said.
Providing this future workforce with quality education and better employment prospects will yield greater economic and social dividends.
With less than 4 per cent of global humanitarian appeals dedicated to education, the report calls for more investment in quality education where children and young people can learn in a safe environment, from pre-primary to upper-secondary, in countries affected by complex humanitarian emergencies and protracted crises.
It said that by current trends, poverty remains the most significant barrier to education globally with the poorest primary school age children four times more likely to be out of school compared to their peers from the richest households.