Improvement science is a framework which groups can use to identify problems within their sphere of influence, test agreed-upon solutions to those problems, and measure the degree to which those solutions have addressed the problems they intended to change. The pathway groups use to do this work is called Plan-Do-Study-Act Cycles, or PDSA. Much has been written about improvement science in terms of what it can look like when implemented. Less has been written about how practitioners in schools have used PDSA cycles and how they reflect on their experiences implementing them. This dissertation is a phenomenological study of four high school math teachers who were recruited because they have multiple experiences using improvement science in their departments, particularly to improve outcomes for students in the classroom related to student discourse and writing. The teachers in this study were interviewed about their experiences and shared artifacts such as planning documents, lessons, data displays, and reflection protocols that have been used in their teams to aid in their implementation of PDSA cycles. The data from the study reveal that teachers perceive improvement science as an iterative set of cycles that support teacher collaboration to solve problems that are within their sphere of influence and can be tested in short periods of time. Teachers also report there are hinderances to implementation, including negative teacher mindsets, unclear vision from leaders, lack of expertise with data literacy, and ongoing change. Benefits are also reported, which include the development of shared practices, embedded professional learning, concrete examples of improvement, and the structure for scaling ideas that work to a wider range of stakeholders. [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.]