This puts them at a higher risk for behavior problems and absenteeism. They are also more likely to have a low self-esteem and feel isolated from their peers. These factors, Hayes and Hemenway believe, could be the reasons that older students within their grades carry guns more often.

Hemenway said he thinks that the problem is not the inherent violent tendencies of these students. Many students surveyed indicated that they carried a gun for protection, because they felt threatened by other students who had guns. Hemenway said he sees this as a problem with the supply of guns to students.

He cited a recent survey in the Boston Public Schools about gun carrying that showed that many students carried a gun, but wished that they did not have to.

Most kids in the Boston Public Schools said that it was pretty easy to get guns, but only 5 percent wanted them to be available. Seventy-five percent want a place where people can't get guns," he said.

Hemenway said that although gun violence is a real problem, with 90 people dying in Massachusetts every day as a result of gun violence, there is not an adequate amount of awareness about it. He said he thinks that studies like this one will promote public awareness.

"The key thing is that what we really need is better data on what is happening and why," Hemenway said, "Anytime someone dies in a motor vehicle accident, we have lots of information on it, and this is not true in gun fatality. In the motor vehicle area, there are a lot of evaluation studies."

Hemenway said that if there were more studies done on factors that affect gun violence, school counselors and clinicians would be better able to assess students' problems and help them. If counselors can better understand the warning signs for those with the potential for violence, they may be able to stop them.

He said school counselors who usually talk to kids about things like drugs and sex should also address the issue of school violence and the risks of carrying guns in school.