This study investigates the role of background characteristics and in-school and out-of-school experiences on public high school dropout rates using data on the 1980 sophomore class from the High School and Beyond Survey. Major findings include the following: (1) dropping out of high school is a complex phenomenon, influenced by an interaction of socioeconomic background characteristics and in-school experiences; (2) some groups of students are more at-risk of dropping out than others, but dropping out appears to be widespread; (3) students in at-risk groups appear to be more vulnerable, both negatively and positively, to in-school experiences than other students; (4) being above the modal age of classmates, and being enrolled in the academic track have the most consistent impact on educational success; (5) early family formation has the most serious negative educational consequences. Implications for the development of federal policies are discussed. Statistical data are included on 18 tables and 13 graphs. The appendices include the following: (1) a description of the High School and Beyond Survey; (2) a discussion of the technical approach used in this report; (3) supplementary tables; (4) description of outcomes, at-risk factors, and high school experiences; and (5) definitions of occupation categories. (FMW)