The purpose of this qualitative transcendental phenomenological study was to understand how high-stakes assessments shape the teacher efficacy and instructional practices of early career secondary mathematics teachers within Title I schools. With the increasing pressure on school districts to meet accountability standards, early career mathematics teachers may feel uncertain about their ability to implement effective pedagogical practices that lead to student success on high-stakes assessments. This study provides insight to school administrators on how to support early career secondary mathematics teachers as they consider the measures of high-stakes accountability within their instructional practices. The study's findings offer context into the experiences of early career secondary mathematics teachers as it relates to best supporting their instructional practices. Drawing upon the elements of American educational policies that drive the focus of accountability measures, the literature review provides insight to the relationship between high-stakes assessments, early career teacher self-efficacy, and their pedagogical practices utilized for student achievement. The following research questions have guided this study: (1) How do early career secondary mathematics teachers at Title I schools describe their efficacy for teaching under high-stakes assessment accountability policies? (2) In what ways do early career secondary teachers at Title I schools describe their experience being required to teach mathematics courses with high-stakes assessments attached to them? (3) How do early career secondary mathematics teachers describe the instructional practices they utilize while preparing students for high-stakes assessment? Recommendations and suggestions for future research are provided to guide school leaders in assisting teachers in attaining measures of high-stakes accountability while best supporting their pedagogical practices and self-efficacy for the field. [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.]