This study explored the relationships among formative curriculum-based measures of reading (CBM-R), student engagement as an extra-academic indicator of student motivation, and summative performance on a high-stakes reading assessment. A diverse sample of third-, fourth-, and fifth-grade students and their teachers responded to questionnaires about student engagement in academic tasks. These questionnaires were collected about the same time as fall CBM-R oral reading fluency and maze screening tasks. Results indicated that fall student and teacher reports of engagement and a composite score of reading competence derived from CBM-R screening tests uniquely predicted student performance on year-end standardized reading tests. Profile analyses indicated that student engagement was associated with better reading performance among students with low competence, suggesting that engagement may be particularly important for increasing student performance for struggling readers. Implications for interventions targeting both student motivation, as well as reading skill development, are discussed.