We examined the degree to which assessment of teachers' instructional and behavior management practices, as measured by the Classroom Strategies Assessment System (CSAS; Reddy & Dudek, 2014), relates to gains in student achievement as measured by the Measures of Academic Progress (Northwest Evaluation Association [NWEA], 2011). Two-level hierarchical linear modeling was applied to achievement scores from 2,771 students in 130 kindergarten through 8th-grade classrooms in 13 urban schools serving students in communities with high concentrations of poverty. Results suggest that teachers' use of evidence-based instructional and behavior management strategies, as measured by the CSAS, were associated with reading and mathematics gains. In general, students in classrooms with higher quality use of evidence-based teaching strategies exhibited greater gains, whereas students in classrooms with lower quality use of effective strategies exhibited lesser gains. Implications of these findings for research and educational practice are presented.