The purpose of this mixed methods study was to understand what effective professional learning looks like and how it impacts teacher effectiveness related to mathematical knowledge for teaching. The three concepts related to this study are teacher's content knowledge, pedagogical content knowledge, and professional learning. A conceptual framework is provided to illustrate the impact of professional learning on mathematical knowledge for teaching; more specifically, teacher's content knowledge and their pedagogical content knowledge. This mixed methods study focused on 3rd-8th grade math teachers in a Louisiana school district through quantitative data analyses of their responses to the Mathematical Knowledge for Teaching and Professional Learning Survey. The survey was designed to assess teachers' perceptions of their mathematical content knowledge, pedagogical content knowledge, and professional learning opportunities. Survey results were correlated to actual student achievement data for math. The qualitative study design utilized a focus group of instructional leaders who work directly with the study's math teachers. Data indicated teachers have a high perception of their content knowledge and pedagogical content knowledge, but there is a statistically significant negative relationship between teachers' perceptions when compared to student achievement in mathematics. Data also indicated instructional leaders recognized this discrepancy between teachers' high perceptions and student achievement. The instructional leaders had differing perceptions about teacher knowledge and the level of impact on student mathematics achievement. The findings of this research study indicate there is a significant positive relationship among all three constructs of content knowledge, pedagogical content knowledge, and professional learning. All three constructs should be considered in order for student achievement to significantly increase. [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/en-US/products/dissertations/individuals.shtml.]