This research report provides information about the school context for learning mathematics and highlights some factors that National Assessment of Educational Progress (NAEP) analyses have found to be associated with effective schooling. Approximately 26,000 4th, 8th, and 12th graders in 1,500 public and private schools participated in the national assessment of mathematics. Data reported from questionnaire responses of students and school principals relate to school socioeconomic and demographic characteristics, student absenteeism, students changing schools, school problems and climate, high schools where students are college bound, impetuses for curriculum and instructional change, home support for academic achievement, mathematics classroom instruction, tracking, and course taking in grades 8 and 12. The most effective schools had students who watched less television, changed schools less often, were subject to only a moderate amount of testing in their mathematics classes (weekly to monthly), took more advanced courses, had positive attitudes toward academics, had fewer problems in the schools, and did mathematics and used calculators more frequently. The effectiveness of private schools was similar to that of public schools in which students, teachers, and parents have positive attitudes toward academics, and where few problems exist. At grades 4 and 8, a more stable student body with students who changed schools fewer times was associated with higher school effectiveness. In summary, students' home background and school socioeconomic indicators were powerful influences on academic achievement in mathematics.