This observational case study employed a qualitative design to investigate the impact of student-centered instructional coaching and self-determined professional development on student engagement in middle school mathematics. Research demonstrates that engaging students in the learning process increases their attention and motivates them to engage in higher-level critical thinking. Teachers who adopt a student-centered approach to instruction increase opportunities for student engagement. Instructional coaches are used as a professional development tool to support teachers with student-centered instructional practices to engage students in their learning. This four-week study involved two sixth-grade mathematics teachers conducting Number Talks in one of their classes of 20-25 students. The instructional coach provided professional development on using Number Talks to improve student growth and engagement. Through the analysis of pre- and post-intervention surveys, focus group interviews, and classroom observations, I identified positive effects of instructional coaching support, perception of student-centered instruction, and coaching around engagement. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]