Our research draws on data from the 2003 Trends in International Mathematics and Science Study (TIMSS). The TIMSS data comprise information on students in two grades in a number of countries, but we utilize only information on 8th-grade students in the United States. Our sample includes 6,310 students in 205 schools with 639 teachers (303 math teachers and 355 science teachers, of which 19 teach both subjects). In addition to test scores in math and science, the TIMSS data include background information on students’ home and family life as well as data on teacher characteristics, qualifications, and classroom practices. School principals provide information on school characteristics.