GIRLS are more devious than boys in their torment of classmates, Australia's biggest childhood study reveals.

Kids who are poor, overweight, Aboriginal, disabled or living with a single mother are most likely to be picked on in the playground, the Australian Institute of Family Studies has found in a survey of more than 4000 children aged 10 and 11.

Three in every five kids had been subjected to "unfriendly behaviour" in the past year, ranging from hitting to name-calling and being left out of social groups.

Boys were more likely to have been pushed, shoved, hit, called names or insulted.

Girls suffered from "covert" bullying, such as nasty note-writing or being left out of play groups.

"The boys are overt and girls are covert," Ben Edwards, the executive manager of the AIFS Longitudinal Study of Australian Children, said yesterday.

"For boys, it's more of a kick in the shins, and for girls there's whispering and excluding.

"It's partly the way kids are hardwired and partly the way they are socialised."

Four in every 10 girls had been excluded from a group, compared to one in three boys.

And 17 per cent of girls had been upset by "note-writing" - a form of bullying experienced by just 12 per cent of boys.

Physical violence - shoving, pushing or hitting - was reported by 40 per cent of boys and 27 per cent of girls.

The federally-funded AIFS study found that migrant children were the least likely to be bullied, with only half the children reporting "unfriendly behaviours" in the schoolyard.

But two out of three Aboriginal and Torres Strait Islander children reported problems, compared to 61 per cent of non-indigenous children with English-speaking parents.

Kids living with a single mother reported the highest rates of bullying - 68 per cent - compared to the 57 per cent of children living with both parents.

Children were most likely to be bullied in small schools with fewer than 250 students, or if they had changed schools in the past two years.

Overweight children were 13 per cent more likely to be bullied than skinny kids.

Dr Edwards said bullied children could turn into bullies themselves, become clingy or disrupt the class.

"They might be fighting with other children or be naughty in class," he said.

"They'll be nervous and clingy, losing confidence and feeling down."

Dr Edwards said children who had a good relationship with their parents and teachers were less likely to report victimisation at school.

But he said girls' "covert" bullying often went undetected and could be harder to manage.

National Centre Against Bullying member Ken Rigby - adjunct research professor of education at the University of South Australia - said most children would not tell their parents they were being bullied.

"Listen and make it easier for a child to talk to you," he said.

"If you always tell a child to get on with it, the child won't talk to you."

Professor Rigby said being left out of groups and games "is one of the most hurtful things that can happen to a child".

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