SUNDAY, Feb. 6 (HealthDay News) -- High school students who work more than 20 hours a week at part-time jobs during the school year may be more likely to have academic and behavior problems, according to a new study.

U.S. researchers analyzed data collected in the late 1980s from 1,800 middle-class teens in grades 10 and 11 in order to compare students who had jobs with those who didn't work.

The study found that working more than 20 hours a week was associated with reduced school engagement, lower expectations for further education, and an increase in illegal activities including stealing, carrying a weapon, and using alcohol and illicit drugs.

These negative behaviors persisted even after such teens reduced their work hours or stopped working, the investigators found.

However, teens who worked fewer hours appeared to experience negligible academic, psychological or behavioral effects, according to the study published in the January/February issue of the journal Child Development.

"Although working during high school is unlikely to turn law-abiding teenagers into felons or cause students to flunk out of school, the extent of the adverse effects we found is not trivial, and even a small decline in school engagement or increase in problem behavior may be of concern to many parents," study leader Kathryn C. Monahan, a postdoctoral research scientist at the University of Washington, said in a news release from the Society for Research in Child Development.

She recommended that parents, educators and policymakers monitor and limit the number of hours worked by high school students.

More information

The Nemours Foundation offers tips on how teens can balance school and work.