This instrumental case study explores how a single teacher whose preservice teacher education program included the practice and implementation of differentiation for all students, gifted pedagogy, and a gifted clinical practicum described the factors that shaped her practice and implementation of differentiation for gifted students in her general education classroom. This study focused on one elementary classroom teacher because the teacher is at the heart of differentiated instruction and makes the decisions about the practice and implementation of differentiated instruction for each student. The combined conceptual framework encompassed the REACH Framework developed by Rock et al. (2008), specifically Quality Indicator 1: The Teacher Variable, Schon's Theory of Reflective Practice (1983, 1987), and Shulman's Pedagogical Content Knowledge (1986, 2013). The following methods were used to ensure data triangulation: semi-structured interviews, observations, short check-ins, email conversations, document/artifact analysis, and member checking. The results of the study showed an overarching theme: The Teacher's Preservice Education Program, and three themes: The Pedagogical Content Factor: Differentiation and Gifted Pedagogy, The Student-Centered Learning Environment Factor, and The Reflective Practice Factor as the factors that shaped this teacher's practice and implementation of differentiation for gifted students. Case findings suggest assertions of teacher self-efficacy and reflection as practice and are represented in a unique diagram showing this teacher's practice of differentiation for her gifted students. [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.]