In halting sentences the Shia boy recalls why he has moved from the mean streets of Doura, in southern Baghdad, to the relative safety of Karrada, a predominantly Shia and Christian area.

“Terrorists came into our house. They stormed our house last week,” he said. “They came in through the roof. We were all at home. We knew them, knew they were terrorists. It was a message. They come into our house, and next time they’ll kill us. We were really scared, so we decided to leave.”

Then he clammed up.

Mona Alwan Hussein, his new headmistress, said that her primary school of 500 pupils had been swollen by 10 per cent this term, almost all of them Shia children from the violent western Sunni suburb of Abu Ghraib or the ethnic battlefield of Doura.

Now Ms Hussein has too many students and too few books — Education Ministry convoys have been attacked by guerrillas and supplies are running short. More worrying than the overcrowding is that the daily violence has leached into the children’s minds. “The kids do less homework, they are less obedient with their teachers,” she said.

Across the capital teachers say that grades are down and aggression up as districts realign themselves along ethnic and religious divides, the separation seeping even into the games children play.

“They are more aggressive and beat each other up more,” said Omar Abu Shams, whose son Ahmed attends a junior school in the mainly Sunni area of Hay al-Jihad in western Baghdad.

“Even in the games they play they’ll split into two groups and play Americans and Mujahidin. Most of the time they choose the runty kid to be an American soldier, then they chase him and beat him. It’s like they are taking revenge.”

Muthana al-Jebouri was shaken when his six-year-old daughter, Manar, who attends the same school as Ahmed, asked him if the family were Sunni or Shia, an issue that had simply never been raised before.

“I felt too ashamed to say, because my wife is Shia and I’m Sunni,” he said. “If I say there’s a difference, I’m creating a division inside the house. I’m really worried about that. So I asked her why she asked me and she said, ‘My friends at the classroom were discussing it, saying, ‘You are Sunni, we are Shia’.”

In the schoolyard yesterday the children’s frayed nerves were all too evident. As pupils gathered for morning assembly behind newly erected concrete blast walls, local youths let off firecrackers, spreading panic. Nawal al-Obeidi, the headmistress, shouted at her staff to get the children inside, but they were fleeing on their own, traumatised by nightly shooting in the area.

“Security is very bad and it is deteriorating,” Ms al-Obeidi said after restoring calm. “The children’s morale is really low. Their situation is getting worse mentally and their health is also declining. Most parents are so wrapped up in securing their houses and lives they forget about the kids’ personal needs. Their schoolwork is worsening, and marks are significantly lower than in previous years. ”

While she has about 75 new students this year — mostly Sunni, many of them children whose parents have been threatened for working for the Government — she is not suffering from overcrowding: more than 100 of her pupils from last year have left the country with their families.

“All the rich kids have left because of the kidnap threats,” Ms al-Obeidi said. Last term four of her students were abducted. Last week two brothers were snatched.

But there is no guarantee of security inside class. In a town just south of Baghdad last week guerrillas marched into a school and shot dead five teachers. Even the new blast walls are a source of fear for Ms al-Obeidi — they were put up because the school will be a polling centre in this month’s constitutional referendum, which could make it a target.

Ms al-Obeidi has, however, managed to nip in the bud any incipient divides among Sunni and Shia children. “I noticed the kids here talking about it, so I told all the teachers to hold long lessons to insist there is no difference,” she said.

“We threatened that anyone doing this that they would be punished, both by God and the authorities. It went well, and we’ve managed to stop it completely in our school.”

In some schools, she said, Sunni teachers would take classes full of Sunni pupils, while Shia staff taught only Shia children, raising fears that trenches dug in this generation of Iraqis will be inherited by the next.

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