All through his daily commute, plodding up roads bumper-to-bumper with families fleeing by truck, car, motorbike and on foot, Dr. Hnak worries that something will happen to his own wife and children before he can return.

“When I get to the hospital,” he said, “the first thing I do is call home to check on my family.”

Schools also have been targeted by Russian and Syrian forces. More than 180 schools are damaged, destroyed or currently housing the displaced.

On a single day in February, local aid groups said, airstrikes hit eight schools around Idlib City, killing three teachers and a student. At least six more students were injured as they tried to evacuate.

But everywhere there are children in need of schooling.

Mr. Ahmad, the teacher at the Return School, once planned to teach philosophy to college students. Now it is a good day if he can hold his young pupils’ attention. The distractions are many: cold fingers, one-meal-a-day bellies, warplanes that snarl overhead. And that is if the children come to school at all.

“I put in so much effort, but with almost no results,” he said. “The students? Most of them are just scared every time they hear the sounds of the planes. We don’t have anything to distract them with or teach them with. We only have this tent.”

For Mr. Ahmad, his wife, Malak, 28, and their young son and daughter, home was the village of Al Iss, outside Aleppo, until they fled two months ago. Ever since, they have lived in a leaky abandoned building near the camp, sharing one room with 17 other people.

Some of the displaced live in tents, but many sleep in half-finished buildings, under olive trees or, in some cases, under nothing. Tents along the Turkish border, which is sealed shut against refugees, hold an average of nine people each, an International Rescue Committee survey found.