This study examines the relationship between teacher and school factors, and mathematics instructional practices following a state-mandated 3-credit professional development course. More precisely, the research examines the relationship between (1) change in Mathematical Knowledge for Teaching (MKT), (2) change in teacher self-efficacy, and (3) administrative instructional leadership and 4th through 8th grade teachers' instructional practices. Multiple linear regression was used to determine the degree of relationship between the teacher and school level variables to mathematics instructional practices subsequent to participation in the Mathematical Thinking for Instruction (MTI) professional development course. The findings indicate that teacher-centered instructional practice five to eleven months after the professional development course is related to AIL and teachers' pre-course MKT score. None of the variables under examination were significantly related to student-centered instructional practice; however, exploratory analysis reveals potential variables for future examination. The results present a picture that the link between teacher and school variables and changes in instructional practice is an intricate one. The findings indicate that the process of changing instructional practice is influenced by many variables and identifying those that are most influential is complicated by several factors. [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/en-US/products/dissertations/individuals.shtml.]