Teachers' voices about the effects of teacher professional development on student achievement are absent from the literature. Researchers have spent decades examining best practices regarding teachers' continued learning. Traditional professional development for teachers is made up of one-time, sit-and-get, workshop-style learning. This archaic method of professional development it ineffective and rarely impacts student achievement and outcomes positively. While the United States spends billions of dollars annually and invests a large percentage of teachers' time in professional development activities, little research exists that highlights a positive effect on student outcomes as a direct result of professional development. Even less research includes teachers' lived experiences with professional development and its effects, or lack thereof, on student learning. Professional development policymakers continue to use archaic forms of professional development, even though new theories of effective professional learning have emerged. This study examined four teachers' perspectives of the inquiry cycle model of professional development in Louisiana regarding its effects on student achievement. Data collection methods focused primarily on teacher interviews. The teachers surveyed for this study were teachers in English language arts within the state of Louisiana who used the ELA Guidebooks curriculum. All the teachers in this study participated in professional development with a national nonprofit organization called Teaching Lab, which uses the inquiry cycle model for professional learning. This study employed Thomas Guskey's Five Critical Levels of Professional Development Evaluation as a framework to examine effective teacher professional development. This framework aligned with Teaching Lab's theory of action coined head, heart, and habits. This study argued that inquiry cycles, as a model of professional development, are effective for increasing student achievement. This study's purpose was to inform change in policies and design of teacher professional development, especially as it affects student achievement in reading and English language arts. This study's results have implications for policymakers, professional development designers and facilitators, district leaders, school administrators, and teachers. This study amplified and elevated teachers' voices about the professional learning in which they engaged and its effects on student learning. [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.]