The implementation of the Pennsylvania Algebra 1 Keystone Exam brought many changes to the mathematics classroom for both teachers and students. The purpose of this case study will be to explore how teachers at a charter school respond to testing requirements through adjustments in how and what they teach and to understand and explain the disconnect between teachers enacted and idealized curricula. The hypothesis is that when courses are tied to high-stakes exams, teachers' modifications in instruction will result in a curriculum and instruction that more closely follows the formal curriculum. As such, this study will focus on answering the following questions: 1.) How are the participating math teachers structuring student learning to prepare their students for success on the Algebra 1 Keystone Exam? 2.) What rationale does each participating math teacher give for explaining why they structure student learning the way they do and how does this rationale connect to preparing students for success on the Algebra 1 Keystone Exam? 3.) In what ways do teachers discuss their intentions to modify both what they teach and how they teach? And why do they make such decisions? This qualitative multi-case study collected data from teacher lesson plans, teacher observations, and interviews. Data was analyzed utilizing a framework that was based on the research questions as well as the literature review streams of high-stakes assessments, teacher autonomy, and the enacted curriculum. Four key findings emerged from this study: (1) The teachers followed good teaching practices and not just test preparation techniques, (2) there was a focus on the process of doing mathematics and not just the product, (3) the teachers were aware that their students were not able to fully engage in a student-centered program of instruction, and (4) the Algebra 1 Keystone teachers were ultimately held to the practicalities of the exam. Based on the findings, it was recommended that administrators should utilize lesson study techniques to further student development, create internalized professional development for their teachers, and implement the CRAMATH method in order to develop abstract thinking in Algebra 1 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.]