Two decades ago, politicians and educators extolled the virtues of part-time jobs for high school students as a way to foster independence, responsibility, and good work habits. Government panels like the 1980 National Commission on Youth also praised part-time work, suggesting it was "the single most important factor" in the transition from youth to adulthood.

Only a year before the Commission's report was published, however, the first of several warnings appeared, challenging the prevailing view that high school students were benefiting from their after-school jobs. That warning came from Temple University researcher Laurence Steinberg, who, in a 1979 report, concluded that after-school work had a detrimental effect on school achievement.

While Steinberg's work--among the most frequently cited in the field--has generally withstood the test of time, he and other researchers are beginning to focus on the 30 percent or more of students who work more than 20 hours during the school week. Growing evidence suggests that teenagers who work more than their peers after school may be more likely to have been disengaged from school before they took a job. Since all jobs are not equal, however, the search is on to define the most optimal work experience for teens.