This action research study identified the effects of learner-centered professional development (PD) and continuous support of effective teaching practices during professional learning communities (PLCs). This study focused on four specific areas--(1) building the teacher's content knowledge through PD, (2) providing support for the implementation of culturally relevant pedagogy during PLCs, (3) providing support for the creation of equitable learning environments with learner-centered instruction, and (4) reducing the math anxiety experienced by the teachers. This mixed-methods research design used pre- and post-survey data of third-grade teachers and students, instructional coach interview responses, and students' post-assessment data to examine how support of teachers' mathematics content knowledge and implementation of culturally relevant pedagogy impacted learning. Data was categorized by themes, and findings indicate that learner-centered PD coupled with pedagogical support during PLCs increases teacher's content knowledge and confidence, while also creating an equitable learning environment for all students. The results of the study suggest that the teacher participants have grown in their comfort level with mathematics and feel more confident with learner-centered instruction. Student achievement also increased due to professional development and support during Professional Learning Communities, as indicated by unit assessments. [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.]