Historically, reforms designed to transform teaching from rote, teacher-centered instruction to progressive student-centered instruction have had varied levels of success. Plentiful research juxtaposes teachers' enacted instruction with the instructional ideals of reform efforts to determine the extent to which teachers' instruction aligns with reform-based science education standards. Discrepancies and continuities are frequently explained by the mediating effects of the instructional context. While this information is valuable and establishes the strong interdependent relationship between context and instruction, little research attends to the capacity of specific contexts to support reform-based instruction. In this dissertation, I explore the liminal space between science reform adoption and reform implementation in a rural, fifth grade classroom. I immersed myself in a veteran teacher's classroom context for two units of study, the solar system and "The Scientific Method." Using Creswell's (2013) interative, inductive approach along with tools from content and discourse analysis, I analyzed interview recordings and transcripts; classroom observation recordings, field notes, and digital photographs; and classroom artifacts to examine how contextual resources and constraints shape the teacher's instructional practices and the extent to which her existing practices align with reform-based ideals and practices. Findings indicate that the teacher's accessible resources (e.g., her own education, school provisions) and professional expectations (e.g., previous standards, school policies) position science as a set of disciplines comprised of a discrete facts that are learned through low-level cognitive tasks of recalling and understanding content and procedural knowledge. Nonetheless, in accordance with the National Academies' call for context-specific instructional support, this study identifies existing pedagogical practices that can be leveraged to achieve instruction that more closely approximates reform-based instructional practices and considers the potential for developing teachers' instructional practices through zones of feasible innovation (Rogan, 2007). I detail the process for identifying zones of feasible innovation for the participating teacher's instruction as a model for designing individual learning trajectories with examples from the instructional context analyzed in this dissertation. Findings and conclusions from this study highlight the need for teacher conceptual change through reflective practices and dialogic interactions. Moreover, this study also suggests school leaders will need to ensure that school structures allow teachers adequate planning and instructional time for science as well as access to technology and spaces appropriate for science activities. Finally, this study establishes a need for equitable access to professional learning opportunities and more research exploring avenues for supporting teachers in their individual, diverse contexts (e.g., open-access, virtual educative curriculum materials), particularly those with limited resources in isolated locations. [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.]