Some 75 million school-age children in crisis areas around the world are in desperate need of educational support, according to a new report by Unicef.
One in four children aged 3-18 - 462 million - live in countries affected by humanitarian crises, the report says.
In Syria, five years of civil war have left 6,000 schools out of use, while in Eastern Ukraine the conflict damaged or destroyed one in five schools.
Refugees are five times more likely to be out of school, the report says.
During times of conflict, girls are two-and-a-half times more likely to be out of school than their male peers, it adds.
The report comes ahead of the World Humanitarian Summit in Istanbul on 23 and 24 May.
A new emergency education fund, called Education Cannot Wait, will be launched at the summit.
The fund aims to raise nearly $4 billion over five years to reach 13.6 million children in need of education in emergencies, Unicef said.
According to the charity, children from the poorest communities who miss school for more than a year are likely to never return.
"During crises, children are particularly at risk of missing out on their education, yet schools provide a safe space and a vital routine for children during times of major upheaval," the report says.
"Education gives children the building blocks to rebuild their lives and, eventually, their country."
Earlier this year, campaigner Malala Yousafzai called for more to be done to educate millions of Syrian refugee children displaced by the conflict.
They risk becoming a "lost generation", warned Ms Yousafzai, who was shot in the head in 2012 by Taliban gunmen for campaigning for education for girls in Pakistan.
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