Zoom out and the picture changes: The children are kneeling on mattresses in a chilly classroom they now call home. An elderly woman cries nearby, wondering whether her mother was killed by Japan’s tsunami. Outside the school, a teacher fiddles with a radiation detector, checking to ensure the levels aren’t high enough to make them sick — or worse.

Behind the smiling faces of thousands of children in shelters across this wave-battered wasteland, experts say there is often serious anxiety as everything these youngsters once held as normal is suddenly anything but.

"That’s what is so wonderfully adaptive about children. They can move very easily into playing or laughing," says psychologist Susie Burke, a disaster response specialist with the Australian Psychological Society. "But that’s not saying they’re not deeply distressed and upset about what’s going on."

Reminders of the tiniest victims are scattered throughout the wreckage: a little girl’s white shoe caked in mud, a red rubber ball coated in dust, a sodden comic book whose ink has run.

As many as 25,000 people may have been killed in the March 11 earthquake and tsunami that devastated Japan’s northeast coast and damaged a nuclear plant, sending radiation spewing into the environment. Tens of thousands are still living in shelters.

For the children, the monster in the closet has been replaced by the monster of Mother Nature: The ground they play on can rattle and crack, the ocean they swim in can morph into a killer wave, the air they breathe might carry harmful radioactive particles.

Ten-year-old Fumie Unoura remembers well the terror of the day. She was sitting in class when the earth began to shake, sending her and her classmates scrambling under their desks for cover. When the rumbling stopped, the teacher shepherded the students outside, where their town had turned to rubble.

"I saw the dust rising up," she recalled days later, standing outside a shelter in the shattered coastal city of Rikuzentakata.

With the tsunami coming, she ran as fast as her short legs could carry her, surrounded by others sprinting for safety.

She escaped with her life but little else. Her home is ruined. She sleeps on the floor of a school gym with her family and more than a thousand other survivors. She misses her Nintendo DS.

Her father, Masanari Unoura, volunteers at the shelter. He worries constantly about what will become of his life, where they will live, how he will clean up the ruins of their home.

"We parents have a lot to think about," he says. "Whereas the kids are basically free."

It is not so simple, experts say. In fact, the disruption of daily life, if prolonged, can be more damaging than the disaster itself, says psychologist Gaithri Fernando, who led a study on how the 2004 Indian Ocean tsunami affected children in Sri Lanka.

Suddenly discovering they have no water to bathe, no bed of their own and no school where they can see their friends can be highly upsetting, says Fernando, a professor at California State University in Los Angeles.

Experts say getting children back into a routine — even an unusual one — is key.

Unoura and his family are doing this. Every morning, they join others at the shelter for group exercise sessions broadcast on the radio. They have breakfast as a family, and then Fumie and her older sister Shiho have time to play until they all meet for lunch. Fumie’s teacher stops by regularly with homework assignments — a source of complaint for his daughter, her father notes with a grin.

That kind of basic structure to the day helps prevent long-term psychological damage, says Burke, the Australian psychologist.

"It gives them a sense that their world is predictable, and when we feel things are predictable, we begin to relax," she says. "A disaster makes us realize or think the world isn’t predictable."

Save the Children, an international aid agency, has set up safe spaces for children to meet and play throughout the tsunami zone, with toys, games, crayons and paper.

"The stories they were sharing with me were about first an earthquake, then a tsunami and now their fears for radiation," says Ian Woolverton, a spokesman for the group. But one fear reigned supreme, he says: "Being alone is the thing they’re most afraid of."

At a shelter in Kesennuma, a group of boys plays basketball while volunteers from a Tokyo church give massages to elderly people on the second floor.

Sixteen-year-old Keisuke Iwate came here to visit his friend Yohei Sugawara. "There are people without homes," Iwate says. "They’re not saying how sad they are, but you know they’re feeling it."

Sugawara, also 16, said that the tsunami ruined the first floor of his house. Then a fire burned it down.

These days, he, too, has carved out a new routine.

"I help out at the refugee center every morning," he says. "And then we go and try to clean up the place where our house was and look for anything that might be left."

He’s better off, he says, than another friend whose parents were killed.

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Associated Press writer Foster Klug in Kesennuma contributed to this report.