The intent of this study was to better understand the impact of teacher practice and student growth mindset on students with disabilities (SWD) proficiency in mathematics. Two research questions were examined: How can redesigning math instruction with consideration for increased class time for targeted instruction and shifts in teacher practice impact teacher support for SWDs in mathematics? How does including lessons, strategies, and activities designed to promote student growth mindset impact the progress of SWDs towards proficiency in mathematics? I employed the tools of improvement science with a mixed methods design to understand the impact shifts to teacher practice by using a new curriculum, redesigning math instruction and developing student growth mindset had on students with disabilities progress towards math proficiency. I analyzed iReady data, team minutes, pre and post unit and student growth mindset survey results. The results suggested that increasing student discussions by incorporating complex instruction, utilizing a curriculum to encourage student discourse and metacognition while employing strategies to develop student growth mindset (participation, explanation and group quiz) had a positive impact on students with disabilities making gains towards grade level as measured by iReady. [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.]