School improvement ultimately rests in the hands of teachers, and the balance of teaching and evaluation of learning is the method for sustained success. In his 2009 book, "Visible Learning (VL)," John Hattie acknowledges this statement and contends that the majority of teachers know what works due to reflexive teaching praxis. Many schools across the nation are implementing the "VL" framework through professional development (PD). This study will focus on the implementation of the "VL" framework through PD in the high-performing Southeastern school district of Suburban County. A mixed-methods inquiry was conducted to learn more about teachers' perceptions of "VL" PD efficacy and preferences for future PD. Qualitative results showed teacher competency improved after "VL" PD but knowledge of "VL" remained incomplete. Quantitative results were not statistically significant but the use of the "Teacher Mindframes Survey" (Murphy, 2020) demonstrated internal reliability for this new instrument. Overall, findings suggested future "VL" PD should focus on generating greater teacher buy-in. One way to do this is by integrating "VL" PD with Adult Learning Theory (ALT) models and practices, as "VL" implementation can be enhanced through the addition of academic coaches and the incorporation of ALT practices. The researchers concluded additional studies are needed to determine best practices for implementing "VL" in schools. [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.]