BEIT LAHIYA (AFP) - Some 200,000 Gaza children returned to school on Saturday for the first time since Israel's offensive, many having lost family members, their home and their sense of security. The UN Relief and Works Agency (UNRWA) reopened all its 221 schools which educate some 200,000 Palestinians in the territory and provided shelter to tens of thousands of people during the fighting. At Beit Lahiya primary school the children swarmed into the wide courtyard with their oversized backpacks, noisily running and playing beneath an upper-storey classroom scorched by an Israeli shell. The compound was struck a week ago and set alight, sparking panic among the 1,600 people who had gone there seeking shelter. Two boys, five and seven years old, were killed and around a dozen people were wounded, including their mother, whose legs were cut off, according to the UN. It was one of three schools sheltering displaced people which were hit by Israeli fire during the war. At another UN-run school nearby more than 40 people were killed by Israeli shelling on January 6. The Israeli military said it had taken fire from in or near each of the buildings, but UN chief Ban Ki-moon called the attacks 'outrageous' and demanded those responsible be held to account. As the hundreds of children were slowly brought to order it soon became clear that many of them bore the unseen wounds of the war, in which more than 1,330 Palestinians were killed, nearly a third of them children. "Come forward if your mother or father was martyred," headmaster Riad Maliha announced through a megaphone to the classes lined up outside for morning assembly. "Come forward if your house was destroyed." More than 20 students walked to the front to register with UN officials so their families could receive aid, including Anas Abbas, a shy 12-year-old boy. "They destroyed our house and killed five of my neighbours. The Jews came very close to us," he said, his brown eyes looking away. Like the other children, he renders his experiences in one-word answers and simple sentences, keeping most of what he has seen to himself. Maliha, the headmaster, says the first few days of school will be given over to counselling, with teachers trying to help the children express themselves. "In the classes the teachers will encourage them to talk about what happened, or to draw pictures or to write about it," he said. UNRWA, which provides basic aid and services to most of the 1.5 million people living in Gaza, employs some 200 counsellors and is looking to recruit more in the wake of the war. "Imagine what the conversations are going to be like," UNRWA spokesman Christopher Gunness said. "There are going to be thousands of traumatised children coming to school today." On the upper floor of the school the children drift in and out of the burned-out classroom, chalk graffitti scribbled on its blackened walls and charred blankets and broken desks littering the floor. In the classroom next door the teacher invites the children to come up to the front and tell their stories. The first boy to volunteer recalls when the house next to his was blown up. "The door was dancing. The windows were dancing," he says as the other children break into laughter. Khitam Aziz, the school counsellor, says the children ask about the scorched classroom upstairs and the holes in the walls left by artillery rounds. "They ask me why they shelled the school, and tell me they worry it will be attacked again," she says. "But we tell them the Jews will not attack the school. They should feel safe. They should play."