This article examines the effectiveness of observable and quantifiable traits in and approaches of school principals in enhancing student achievement. Data were gathered on 2,048 fourth-grade students in 96 public primary schools in Leon, Mexico; Belo Horizonte, Brazil; Buenos Aires, Argentina; and Santiago, Chile. The UNESCO/ORELAC (United Nations Education and Social Council/Regional Education Office for Latin America and the Caribbean) language and math examinations were administered to each student in the sample, and school-level data were collected from principals, teachers, and the parents/community. Variables included the principal's education, experience, priorities, leadership style, and relationships with teachers. I estimated equations using hierarchical linear modeling. Results indicated that both community environment and instructional roles for principals were associated with increased student achievement. Important variables related to higher student language and math scores included the principal being at a school more years, emphasizing student evaluation, creating a better work environment for teachers, and spending more time promoting community events with an academic orientation. Variables negatively related to student achievement included a lack of parent participation, high teacher turnover, and principals focusing on student discipline. (Contains 13 tables and 6 notes.)