A new analysis of a 2005 survey of American schoolchildren, conducted by researchers at the Loma Linda University, California, has identified factors that may help pick out kids who are most likely to carry weapons to school.
According to the researchers, the study might help in improving school safety.
In the study, 13,707 students participated - 6,664 (50.5 percent) were male and 7,193 (49.5 percent) were females.
The analysis, carried out by Emmanuel Rudatsikira and his colleagues, showed that the variables most associated with the carrying of weapons were being male and being a member of certain self-selected racial groups.
Researchers found that pupils who identified themselves as white were more likely to carry weapons than those who identified themselves as black.
"We do not believe that there are any inherent genetic differences that determine race and that affect the way that adolescents behave," the authors said.
"We take the view that racial categorization has facilitated the distribution of social and economic resources that may consequently influence adolescent behaviours and perceptions toward violent behaviour," they added.
The results were surprising. The researchers stated that as the poor are likely to live in violent neighbourhoods, they would be more likely to feel unsafe and therefore carry weapons to school.
"We would have expected that minorities such as African Americans, being largely disadvantaged in the United States, would be more likely to bear weapons." Rudatsikira said.
"If black students felt less threatened at school, it's less likely they'll carry weapons. Alternatively, the schools they attend may be more vigilant in policing weapon carrying as a possible result of high violence and weapon bearing in black neighbourhoods," he added.
Other factors linked to weapon carrying were substance use, depression, having been a victim of theft or property damage at school, having been raped, having been threatened with a weapon or having been involved in a physical fight.
The study is published in BioMed Central's open access journal Annals of General Psychiatry.