The purpose of this study was to investigate the importance of teachers' professional preparation in mathematics and science, particularly with respect to student outcomes as measured through student test scores. The study uses the base-line data collected in 1988 for the National Education Longitudinal Study, a national study of 24,599 students in the eighth grade. The following factors affecting science and mathematics learning are discussed in detail: student characteristics including attitudes, students' plans for the future, student behavioral characteristics, gender equity, and minorities; school environment characteristics including attention given to science and mathematics, assessment, and resources; teacher characteristics and practices including teacher preparation, cooperative learning, texts, and homework; and family environment. Other topics discussed include: teacher characteristics as measured through transcripts including types of courses taken and grade point averages; teachers' backgrounds and the classroom environment including content covered by teachers, approach to homework, teachers' use of time, teachers' attitudes, patterns in teacher and student assignments, and influence of teachers on student attitudes; and teacher's background and student outcomes including inequalities in teachers assignments and student outcomes and multiple regressions. Ten appendices include: a description of NELS:88; the reliability of survey estimates, a comparison of transcript-based measures against teachers' self reports, academic degrees, and teacher certification. Contains 73 references. (JRH)