The purpose of this case study was to explore teachers' pedagogical beliefs about student learning and achievement in mathematics. The participants included three classroom teachers who taught mathematics from one public charter school in Southern California. Data collection included two sets of interviews, field notes, samples of lesson plans, student work samples, and assessments. Interviews asked participants to reflect on their pedagogy, how they described their role during mathematics instruction, how they assessed their students in mathematics, what assessment tools and materials guided their planning, and how they described student achievement. Results revealed one overarching theme, Complexities of Teacher's Role and Pedagogical Stance, and five sub-themes: Curriculum and Lesson Planning, Professional Development, Teacher Collaboration and Mentoring, Student Learning and Assessment, and Educational Policy and School Accountability. Overall findings stated that participants considered their role as a "facilitator" in the classroom and "took pride" in collaborating and mentoring with their grade level colleagues during lesson planning to improve student achievement. Participants also revealed their beliefs changed over time due to a combination of factors (i.e., professional development experiences) that impacted their pedagogy. Teachers also assessed student achievement using a variety of measures such as progress monitoring and informal assessments. These findings indicate that teachers' pedagogical beliefs were largely shaped by the ways teachers reflected, collaborated, planned, and delivered mathematics instruction. [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.]