This paper explores how high schools, through their structures and organizations, may influence their students' decisions about whether to stay in school until graduation or drop out. Traditional explanations for dropout behavior have focused on individual students' social background and academic behaviors. What high schools do to push out or hold onto their student has been systematically ignored. Using a sample of 3,840 students in 190 urban and suburban high schools from the High School Effectiveness Supplement (HSES) of the NELS:88 study, researchers used hierarchical linear-modeling methods to examine school effects on dropping out, once students' academic and social background had been taken into account. Findings center on three features of secondary schools: curriculum, school size, and social relations. In schools whose curricula are composed mainly of academic courses, with few nonacademic courses, students are less likely to drop out. Similarly, students in schools enrolling fewer than 1,500 students more often stay in school until graduation. Most importantly, students are less likely to drop out of high schools where relationships between teachers and students are consistently positive. The impact of positive teacher-student relations, however, is contingent upon the organizational and structural characteristics of high schools. (Contains 39 references.) (Author/RJM)