This qualitative phenomenological study explores teachers' beliefs regarding students' physical activity and the effects on academic performance in a low-socioeconomic school district in a Midwestern state. This study investigates the importance of physical activity through Albert Bandura's Social Cognitive Theory of Self-Efficacy and John Dewey's Theory of the Whole Child. Fifteen teachers were interviewed from a low-income Midwestern school. The findings from this study show that teachers believe that physical activity is critical to students' academic success, mental and physical health, and social skills. The need to promote physical activity is more urgent to increase educational opportunities in low SES schools. However, teachers express concerns about losing instructional time while increasing physical activity amid the continuous push for academic accountability and standardized testing. The study reveals wide-ranging implications for policy and practice. The study contributes to the current literature by focusing on teachers' perceptions of some specific and important needs of low-income students that are often overlooked in the debate on school reform today. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]