The Hassan Sham camp, a sprawling refuge for displaced people east of Mosul, is growing by the day as people flee fighting in the city, which Iraqi forces are trying to wrest from ISIS control.

Among the tents, toilets and food distribution centers, aid workers have set up classrooms in tents. There's a play space where little girls are jumping rope in the chilly sunshine, while hundreds more children sit in class.

They're learning English, Arabic, arithmetic — most for the first time in years.

About a million people have been living under ISIS in the city of Mosul for more than two years. Hundreds of thousands of them are children. As security forces press an offensive on the ISIS-held city, children are among those escaping and living in camps for the displaced.

A mother and her son — who don't give names because they're still afraid of ISIS — talked about how the little boy, who's about 10, used to enjoy school.

"Yes, I used to like it," he said. "But I stopped going since they came."

ISIS arrived in summer 2014 and changed the curriculum.

"They showed us how to make a grenade, how to load a machine gun," the boy said. They also incorporated bullets and bombs into math puzzles, and showed children how to commit acts of violence.

He went home and told his parents.

"I told them one day about the lessons I was getting in school, and my mom told me, 'Stop going,'" he said.

But his mom says removing him from class didn't protect him from exposure to ISIS.

"They would tell the children, 'Come and watch our heroic acts,'" she said. "They would slaughter people in public. The children were terrified. They should be playing, and instead it was blood, blood everywhere."

Many of the people now coming out of Mosul speak of ISIS deliberately indoctrinating children — at school, at summer camps, even at public executions, which they would encourage children to participate in.

Iraqi teachers working with the displaced children say their ordeal is reflected in their behavior. Zainab Abdelaziz steps out of a math class to talk.

"They're rough," she said. They are violent, she explained, especially the older ones. She's experienced, and knows that Iraqi children saw violence even before ISIS. But she said these children are faring worse than those who were not exposed to ISIS.

Still, she said, "They can change." When they go to school, learn about tolerance, interact with other kids, she said, they change.

International aid agencies say setting up basic classrooms should be part of emergency help for children caught up in conflict. The Hassan Sham camp tents are run by the Norwegian Refugee Council with help from the United Nations.

"Even if it is a tented school, knowing that every day they can go there, that it's a safe space where they can meet other children, they can go back to some learning practices, it's of critical importance," said the U.N.'s Regional Child Protection Specialist Isabella Castrogiovanni.

She has seen the benefit around the world of providing regular school access to children in conflict regions. In Afghanistan, after the fall of the oppressive regime of the Taliban, she recalled lines of girls waiting to go back to school for the first time in years.

"I remember those lines, huge lines of girls, all getting ready to go to school, and this has a huge impact in the psychological well-being of children," she said.

I asked that little boy in the camp how it felt to be back at school.

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