They are among the most traumatized children to test Australia's schools: hundreds of Sudanese children - many of them Sudanese Christians - are now resettled in Australia, after fleeing a brutal civil war in their homeland and living in refugee camps in Egypt, only to face new challenges.
Beneath the playground laughter, some of these children bear the mental scars of seeing friends and relatives tortured and murdered.
Here at Saint Joachim's Primary school in Sydney, there are more than 20 Sudanese students. Fitting in to a strange, Western society is not easy, especially for these children, who have endured years of uncertainty and upheaval. They have come from one of the least-developed countries in the world, to one of the most modern.
The school principal, Warren Hopley, says the abuse they have suffered has eaten away inside them like a cancer. "Many of them aren't aggressive but they are traumatized in so far as they really find it hard to focus, they find it hard to concentrate," he said. "They've been treated so badly and hurt so badly that their whole self-esteem is a major problem. They're trying to find their own identity and they're not sure what that is."
These five- and-six-year-old Sudanese refugees are academically far below their classmates.
They are taught separately and receive intensive tutoring, but, says Principal Hopley, it is a real struggle.
"Their concentration span is so short and their learning capacity's not great," he added. "For example, today they're learning animals, whereas the rest of the class is over to the other side of the room and they're at the stage where they're writing sentences and they're at a significantly higher level in terms of reading and writing."
One 10-year-old, Adau, remembers bomb attacks on her village.
"In Sudan, there were small airplane come up there and then they want to kill the people that in Sudan," she said. "Yeah, that's why we moving to come to Australia here with airplane."
The Australian government issues around 12,000 refugee visas every year. It provides a network of support from accommodation to health and psychological services to these newcomers. But with a government-funding squeeze on schools across Australia, money for the specialist services that refugees need is being cut, along with mainstream services.
Charities and churches play a crucial role in helping newcomers to adapt to a strange country.
Anna Dimo is a teacher's aide. She fled Sudan after being imprisoned and spent a decade in a camp near Cairo before landing in Sydney. She says the young refugees face huge challenges.
"When they came from Sudan with their own culture, when they arrive in Egypt - other culture. When they come in Australia - three cultures. It's difficult for the children to learn," said Ms. Dimo. "But now the children - they're bright. They got in this school and a teacher to teach them and they understand more and they're very bright."
Here in central Sydney, older students attend an intensive English-language course as they prepare to enter mainstream high schools. Migrants from South America, Russia and Indonesia sit alongside arrivals from Africa, Iraq and Sri Lanka.
The deputy principal of the school, Kathie Power, says the determination of the refugees to succeed is an inspiration. "They're very resilient and that really amazes us on the one level," she said. "We can learn a lot from them because, you know, we're living in a country where we're fairly well off here and we've got lots of things that they don't even know about and often it's a shock for us to realize what we take for granted here."
Suha is 15 and wants to make the most of her opportunities in Australia. Her aims are simple - to go to high school and become a doctor in her adopted country. "It's so easy to learn English because I learn English in Sudan - a little bit of English, and I have better English than when I came here and I will go to Barewood Girls High School and I will be doctor," she said.
Australia since the World War II has been built on waves of migrants, and refugees - more than half a million - have played an important part in the country's development, a sign that these Sudanese children will have a place in their new home.