In 2002, the No Child Left Behind Act (NCLB) called for "highly qualified" teachers in every classroom in order to increase student outcome and provide equitable learning opportunities to all students including poor and minority students. content and pedagogical knowledge before they come into the classrooms. However, research evidence suggests that the relationship between teachers' background characteristics and student achievement is still tenuous and mixed (Darling-Hammond and Youngs, 2002). Moreover, it is hard to interpret these mixed results because the mechanism by which teacher qualifications influence student achievement remains unknown. In spite of much research on the relationship between instructional practices and student outcome, not many of them consider instructional practices as a mediator between teacher background characteristics and student achievement. Using structural equation modeling (SEM) and the National Center for Educational Statistics's Early Childhood Longitudinal Study-Kindergarten Cohort of 1998-1999 (ECLS-K), the author examined direct and indirect effects of teacher background characteristics on student achievement. Indirect effect is used to describe the teacher's effects on student achievement mediated by various instructional practices. Assuming that teachers acquire the content and pedagogical knowledge from prior educational or teaching experiences, the indirect effect can show how the "knowledge" of what to teach and how to teach is connected to the "practices" of what to teach and how to teach. With this approach, the total effects of teacher quality on student achievement would be substantially less obscure. Three tables and one figure are appended.