Administrators have cracked down on physical aggression in schools, enforcing zero tolerance policies for fighting between students.

CNN: Could your child be a bully?

Juvonen's study, however, found boys and girls spread rumors to boost their social status -- and that both genders use physical aggression to assert power.

CNN: Could your child be a bully?

The most prevalent challenging behaviour was verbal aggression (cited by 77%), followed by physical aggression (57%), bullying in person (41%) and breaking or ruining other pupils' belongings (23%).

BBC: Disruptive behaviour rising, teachers say

Juvonen and her team recently followed more than 1, 800 students through seventh and eighth grade to determine how physical aggression and the spreading of rumors played a part in social prominence.

CNN: Could your child be a bully?

In its annual statement, the trust revealed that during 2005-2006, there were a total of 290 incidents of physical and verbal aggression by the public to its crews.

BBC: NEWS | UK | Wales | South East Wales | Ambulance crews facing violence