In response to a shift to high-stakes assessments, teachers are changing their instruction and approaches away from research-based formal training on best practices teaching in response to the stress and pressure this shift has created (Avalos et al., 2020; Gonzalez et al., 2017; Musoleno & White, 2010). More research is needed on teachers who make the choice to exercise their agency or ability to implement practices in their mathematics classrooms which align with the effective pedagogical methods. BarajasLopez and Larnell (2019) described acts of creative subordination as an avenue for teachers to push back against formalized curriculum assessments and reassert their power. This explanatory sequential mixed-methods study explored mathematics teaching self-efficacy and perceptions of school goal structure as factors influencing middle grades mathematics teachers' (MGMTs) goal orientations. Quantitative data were collected in Phase 1 through an online survey with MGMTs and was used to select participants for Phase 2 of the study. Qualitative data were collected in Phase 2 through semi-structured interviews with five mastery-oriented middle grades mathematics teachers who perceived their school environment as performance oriented. To understand current MGMTs, a standard regression was conducted. Results indicated that mathematics teaching selfefficacy, education, and teaching experience accounted for 29.1% of the variance in MGMTs mastery goal orientation. Additionally, a second regression model indicated that both perception of performance school goal structure and mastery school goal structure accounted for 35.9% of variance of performance goal orientation. Several key findings emerged from values and structural coding the qualitative data in Phase 2. MGMTs valued their students' effort, autonomy, relationships, and self-efficacy. These values were characterized by practices that reframe mistakes, pushed student autonomy, communicated via verbal feedback, and encouraged students to grow in their learning. [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.]