International tests indicate that students in the United States rank lower in mathematical achievement than students in many other countries (NCES, 1998; OECD, 2014). More than one-quarter of American 15-year-olds do not reach a baseline proficiency in math and do not have the requisite skills to effectively participate in day-to-day life decisions (OECD, 2012). One cause of low math performance is student disaffection (Lewis, 2013a, 2013b; NCES, 2013b), which teachers are uniquely positioned to combat. This intrinsic retrospective case study investigated the experiences of three high school teachers in a professional learning community (PLC) aimed at disrupting students' math disaffection. Students' responses to these teachers' efforts and the impact of a student-centered teaching approach on students' motivation, engagement, and participation were also captured. Knowles's theory of andragogy and self-directed learning formed the theoretical framework for this qualitative inquiry. Literature across the threads of students' historical math experiences, mathematical disaffection, alternative pedagogies to teaching math, and teacher professional development informed this study. In this case, high school students' math disaffection was effectively disrupted through a flexible curriculum that engaged students in project based learning with a focus on 21st century skills. Students who contributed to designing their own learning responded with higher levels of motivation, engagement, and participation. This study revealed that teachers in a self-directed PLC experienced growth in creativity and a transformation of their perceptions of their roles as educators. Findings from this study inform teachers and districts seeking to improve students' mathematical engagement and implement effective teacher professional development. [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.]