In a corner room at the Kama Elementary School, 30 children wait in silence for news that might never come.

It was home time when the tsunami swept through Ishinomaki, north-east of Tokyo, on Friday - but the parents of these boys and girls did not arrive to collect them. Every day since then, they have sat here patiently, passing the time by reading books or playing cards, hoping their mothers and fathers might yet turn up at the school gates.

Some may be aware that their parents went missing when the tsunami struck: the younger ones may have only suspicions. But the silence is infectious and none seems to want to break it.

The miserable plight of these children, aged between eight and 12, is heightened by the sound of other children noisily playing in the corridor outside - schoolmates who still have their parents due to a fluke of geography or timing.

Masami Hoshi, the sports teacher, has devoted his efforts to trying to obtain enough food for the 657 people now living in the four-storey building. He is also trying to locate missing students and their parents, with some successes, but these 30 children are still alone. "The tsunami came just when the parents of the middle classes were arriving to collect their children, so we managed to get them inside and to safety," Mr Hoshi told The Daily Telegraph.

"The younger ones had left with their parents a little earlier. The ones who went to homes behind the school probably survived. Those who went that way [he points across a muddy playground toward a road littered with debris] probably didn't make it."

Even though the school is a mile from the sea wall that was meant to protect Ishinomaki, the torrent of water raced into the ground floor of the building. A line on the wall shows clearly how high it reached: it is chest-high on an adult and above the heads of most of the pupils here. "Some of the parents were sucked back out across the playground when the waters receded so we grabbed fire hoses and threw them out and dragged them all back in," said Mr Hoshi.

The school has no power, heating or running water. The swimming pool to the rear is brimming with murky water that families are using to wash the mud off shoes and clothing.

Mr Hoshi says they are waiting for food to be delivered, but have no idea how long that might take.

Children's pictures are still on the walls, showing images of mountains, animals and a boat on the ocean. A row of smocks hangs on pegs by the door. In the corridor, a middle-aged woman keeps up a constant - but near hopeless - effort to sweep it free of mud and debris. In one room, 31 people cram together to sleep on cushions and blankets. There has been light snow for the past two days and temperatures inside the school are below zero for much of the day.

Nearly 163,000 people are listed as residents of Ishinomaki and, so far, 425 have been confirmed dead, with another 1,693 missing. It may take many weeks to discover the fate of the children's parents and brothers and sisters, if they are found at all. Meanwhile, they carry on their silent games in the first-floor classroom.

We are not allowed to enter the classroom or speak to the children, to prevent more reminders of the disaster that has befallen them - and the sound of a door sliding open behind them might falsely raise their hopes that their parents have at last arrived to take them home.