“Children and adolescents are super vulnerable to being trafficked, whether for sexual exploitation or for household work,” said Mr. Steinlechner of Unicef. “Right now we are still busy delivering aid, but we are aware that trafficking is happening under our noses.”

By puberty, many Rohingya girls are married off, freeing a family from having to subsidize another child. By the time the average teenage girl arrives in the camps, she has two to four children of her own, according to United Nations estimates.

Rohingya boys have other options, like working in tea shops or providing manual labor for construction sites and road crews. (Unlike girls, they also can use their free time to play soccer with a ball of rags or fly tattered kites.)

Sayed Alam, 12, who arrived in Bangladesh nearly four months ago from Myanmar, makes $1.20 a day pulling in fishing nets on a beach not far from the refugee camps. It’s a job he also worked in Rakhine, he said, just like his father and grandfather before him. He has never attended school.

What does Sayed hope to do when he grows up?

“I don’t have any dreams,” he replied. “I will take whatever job I can find.”