The data and analyses presented in this report are from the first (1980) wave of a longitudinal study of U.S. high school seniors and sophomores. A total of 58,728 students from 1,016 high schools participated in the survey. Special emphasis was placed on Hispanic students, Catholic schools with high proportions of black students, non-Catholic private schools, public alternative schools, and private schools with high-achieving students in order to conduct special studies of those populations. The findings of this baseline data suggest that labor force activity is a widespread phenomenon among teenagers, far exceeding what was commonly believed to be the prevalence of this behavior. While some differences were found among ethnic and gender groups in the propensity to work and the amount of time spent at work, school grade consistently had the greatest impact on all aspects of work behavior, from hours spent at work and hourly wages to the type of job held and amount of training received on the job. The comparison of sophomores and seniors reveals a distinct trend toward greater likelihood of employment, more time spent at work, higher wages, and holding jobs that are performed in a structured organizational setting and away from the family environment. (Numerous tables present data by race, sex, school grade, ethnic background, type of employer, unemployment, etc.) (KC)