FRIDAY, June 19 (HealthDay News) -- A school-based prevention program begun in the early grades can reduce rates of substance abuse, violence and early sexual activity, says a U.S. study.

The study included students at 20 public elementary schools in Hawaii with below-average standardized test scores and diverse student populations. About 55 percent of the students at the schools received free or reduced-price lunches.

Some of the schools were randomly selected to implement an intervention program called Positive Action (PA), consisting of daily 15- to 20-minute interactive lessons on topics such as responsible self-management, getting along with others and self-improvement. The program was given to students for about one hour a week beginning in the first or second grade.

By the time students reached fifth grade, those exposed to the PA program were about half as likely to report engaging in problem behaviors as those who weren't exposed to the program. The study appears online and in the August print issue of the American Journal of Public Health.

"This study demonstrates that a comprehensive, school-wide social and character development program can have a substantial impact on reducing problem behaviors of public health importance in elementary school-age youth," principal investigator Dr. Brian Flay of Oregon State University said in a news release from the U.S. National Institute on Drug Abuse.

He said a follow-up study is planned to examine whether the positive effects of the program continue as children grow older.

"This study provides compelling evidence that intervening with young children is a promising approach to preventing drug use and other problem behaviors," Dr. Nora Volkow, director of the institute, said in the news release. The agency supported the study.

"The fact that an intervention beginning in the first grade produced a significant effect on children's behavior in the fifth grade strengthens the case for initiating prevention programs in elementary school, before most children have begun to engage in problem behaviors," Volkow said.

More information

The American Academy of Pediatrics has more about children's behavior.