Figures gathered by the UN show that children make up more than half of all Syrian refugees.
More than 1.9 million Syrians have left the country so far.
And aid agencies say they expect hundreds of thousands more to seek asylum elsewhere in the coming months.
Shanthi Benjamin reports.
In Jordan's fourth largest city, children take part in classroom activities: reading and writing are all part of the daily routine.
But this is not a typical city.
It's Zaatari -- the world's second-largest refugee camp, and home to more than 120,000 Syrian refugees, over half of whom are children.
UNICEF's director of Emergency Programs, Ted Chaiban, says Syria is a children's crisis.
"The Syria crisis response is the most important crisis that the world is dealing with for children today, and continues to be so. There are over four million children that are affected in the sub-region."
Figures gathered by the UN show one million children have fled Syria's borders since fighting broke out almost two and a half years ago.
Three quarters of them are under 11 years old.
For eight year old Syrian refugee Aya, leaving was unavoidable.
"They began to bomb our house. We couldn't stay there any longer, we were crying a lot."
Aya hopes she will return one day.
Many of these children arrive with their families, walking long distances to get to safety.
Records kept by refugee camps show more than 3,000 children have crossed Syria's borders unaccompanied or separated from their families.
Inside refugee camps across the region, they try to restore some kind of normality.
But there are fears these children could become Syria's lost generation.
The UN says more than 150,000 children have received psychosocial assistance.
Andrew Harper is the head of the UNHCR in Jordan.
"We also have to take into account that these children have seen horrific scenes inside Syria. Often their homes have been bombed, they've lost family members and, most importantly, they don't know what's happening next, they do not how long they will be in the camp."
He says the families in the camps just want to go home and resume their lives.
But fears of chemical attacks and ongoing fighting means more refugees will be leaving.
"There's not one indicator that would give us any sign of hope in relation to Syria and the refugees reflect that as well. We're going to see hundreds of thousands more Syrians fleeing in the next months as the fighting intensifies."
In two and a half years of war, more than 1.9 million Syrians have left the country.
Despite the hardships in the camps and the upheaval in his life, 10 year old Mohammed is hopeful he will one day be able to return home..
"When I go back to Syria I will go and check on my home and then I will go see my grandmother Sawad and grandmother Handa who was injured when rockets destroyed her kitchen."
It's a hope echoed by one million Syrian children.
