School bullies who are not picked on themselves make the happiest, healthiest pupils, according to a survey.

Researchers found that these "pure" bullies enjoy going to school, and are least likely to take days off sick.

But they are also in the minority, as most bullies are, in turn, bullied themselves.

The research, by the Economic and Social Research Council, reveals that parents of bullies who escaped victimisation reported their children had significantly fewer coughs, colds and tummy aches than other pupils.

It also shows these "pure" bullies are less likely to invent illnesses.

Sleeping problems

Professor Dieter Wolke, from the University of Hertfordshire's department of psychology, said the study showed the benefits of bullying were not restricted to health alone.

"It also seems that physical pure bullies sleep well at night, with 65% reporting fewer sleeping problems than bully victims," he said.

A total of 2,377 primary school pupils in north London and Hertfordshire were questioned for the survey.

Almost half of them said they had experienced verbal bullying, while a quarter said they suffered physical attacks several times a week - three times the level in German schools.

Fewer than 3% admitted to being habitual physical bullies who carried out attacks on others on a weekly basis.

But a greater number said they tormented others "frequently", although almost all of them had suffered bullying themselves.

The research also shows that boys launch both more verbal and more physical attacks on others than girls do, and that bullying is more likely to occur in small communities and classes.