So in September 2011, six months into the uprising against President Bashar al-Assad of Syria, the parents sent the three children — then 15, 13 and 11 — away from home in Hama Province with about $425 and a tent sewed out of Chinese rice sacks. The children have lived on their own in Jordan ever since. The eldest, now 17, picks vegetables for $8.50 a day when he can; the girl has learned to cook; the younger boy kicks a ball or plays cards. He has no actual cards, so he made his own, writing numbers on scraps of paper.

“I used to just be a child — now I’m the head of the house,” said the 17-year-old, who spoke on the condition that he not be identified to protect his family in Syria. “I need a budget and to manage my money. I never thought of that before.”

As the Syrian civil war rages into its third year, nearly one-third of the population of 22 million inside Syria needs humanitarian help, and 1.4 million have fled their homeland altogether. Of about 500,000 seeking shelter in Jordan, about 55 percent are under 18. Their troubles and challenges — years out of school, trauma from having witnessed the killing of relatives, sexual abuse — mirror those of their peers struggling to survive in tents and hideaways in Turkey, Iraq, Lebanon and Syria’s own shattered communities.

These children, the next lost generation, make up a particularly troubling category of collateral damage from Syria’s chaotic conflict, which has left 70,000 people dead. There is Ahmad Ojan, 14, who wanted to be a teacher, but now spends his days peddling tea in Jordan’s sprawling Zaatari refugee camp. And there is Marwa Hutaba, 15, who still hopes to be a pharmacist, but is increasingly worried she might be married off to a wealthy foreigner — like the 14-year-old who disappeared from school after “getting engaged one day and married the next.”

“When you talk to them about the future,” said Carolyn Miles, chief executive of Save the Children, “they can’t see beyond, frankly, the next day.”

Children have been streaming across Syria’s borders for more than two years, thousands of them separated from their families. Even those accompanied by their parents arrive traumatized: a recent study by a Turkish university found that three out of four Syrian youngsters had lost a loved one in the fighting.

Before the war, more than 90 percent of Syrian children were enrolled in school; in Jordan about one in three of the refugees ages 6 to 14 attend class. The rest are left to learn the life of an exile, where guile and aggression matter more than books and tests. Where there is little to look forward to, only now.

In Zaatari, children dodge tear gas at near-daily demonstrations. They shake down water tankers to get their buckets filled first. They throw stones at aid workers. Gangs have formed, looting doors and windows from trailers and busting through fences.

“Nine-year-olds are coming to the swings armed: that’s a serious issue that we have to deal with every day,” said Jane MacPhail, Unicef’s coordinator for Jordan’s camps. “Your brain changes. Your ability to assess risk goes. What we have to do is reconnect these kids’ neuropathways to their emotional brain. Otherwise we’re going to lose this generation.”

This small desert nation of six million opened its doors to the newcomers but was quickly overwhelmed as they gobbled up jobs, taxed scarce water resources and forced schools into double shifts. About two-thirds of the refugees are squatting in Jordanian cities and villages, but the pathos and problems are most profound in Zaatari, where families live in row after mind-numbing row of tents or trailers, each day an endless cycle of finding food and water, clearing dust and debris, waiting in lines. The camp opened last July and now sprawls across five square miles, costs $1 million a day to run and has a population of perhaps 120,000 — by far the region’s largest hub of refugees.

It is a vast jungle of humanity, and disorder. Electricity is pirated. Rations are brazenly bought and resold right outside distribution centers. Riots break out many mornings at three sites where the World Food Program hands out half a million pieces of pita, as boys scale barbed-wire fences to skirt the lines.

It is home, school, play — life — for these displaced children of Syria.

Ahmad Ojan, 14, whose father died a decade ago, arrived with his mother and several siblings three months ago from Dara’a. Each morning, just after 6, he heads to the bread line with a thermos of hot tea, which he sells for 15 cents a cup.

“Chai b’hayl,” tea with cardamom, he calls in a slightly mournful wail. A few other boys pass with similar thermoses. An old man has one, too.