There's been a sharp drop in the percentage of America's children being bullied or beaten up by their peers, according to a new national survey by experts who believe anti-bullying programs are having an impact.

The study, funded by the U.S. Department of Justice, found that the percentage of children who reported being physically bullied over the previous year declined from nearly 22 percent in 2003 to less than 15 percent in 2008. The percentage reporting they'd been assaulted by other youths, including their siblings, dropped from 45 percent to 38.4 percent.

The lead author of the study, David Finkelhor, said he was "very encouraged."

"Bullying is the foundation on which a lot of subsequent aggressive behavior gets built," said Finkelhor, director of the University of New Hampshire's Crimes Against Children Research Center. "If it's going down, we will reap benefits in the future in the form of lower rates of violent crime and spousal assault."

Finkelhor noted that anti-bullying programs had proliferated and received funding boosts after the 1999 Columbine High School shootings.

One of the largest of these initiatives is the Olweus Bullying Prevention Program, which has been implemented in several thousand U.S. schools. It is a comprehensive program that includes forming an anti-bullying committee, training staff to intervene immediately if they observe bullying, and meeting with students and parents when problems occur.

Marlene Snyder of Clemson University's Institute on Family and Neighborhood Life, who is director of development for Olweus, said the survey was heartening to those in the anti-bullying field but not cause for complacency.

"The decline is not happening everywhere," she said. "It's in schools where adults really understand how detrimental this conduct can be and have made a conscious effort to bring these numbers down."

The findings by Finkelhor and his co-authors were based on two national surveys of children ages 2 to 17 conducted five years apart - the first in 2003, involving 2,030 children, and the second in 2008, asking the same questions of 4,046 children. The findings were published this week in the Archives of Pediatrics & Adolescent Medicine.

Children aged 10-17 were interviewed directly about various forms of violence and victimization they had experienced. In the cases of children younger than 10, parents or other caregivers were interviewed.

The researchers said the biggest declines in the various forms of violence and bullying were among children from low-income households.

Snyder said this finding meshed with observations by the Olweus staff.

"Many of the grants have been awarded to large inner-city schools where crime and violence rates had been high and economic conditions were low," she said. "We've seen that when those communities have had the money, they could be successful."

Overall, the findings by Finkelhor and his co-authors were positive - and came on the heels of a major federal study documenting an unprecedented decrease in incidents of serious child abuse. That report, the National Incidence Study of Child Abuse and Neglect, found that incidents of serious physical, sexual or emotional abuse dropped by 26 percent from 1993 to 2005-06.