Relying on a teacher-level randomized experiment with a sample of 87 middle and high school teachers, this study was designed to examine the implementation and impact of MyTeachingPartner-Secondary delivered by local coaches who were trained and supported by the program provider. Due to disruptions caused by the COVID-19 pandemic, implementation of the 2-year program during the first year (2021-22) was weak, and only four of six study districts continued to participate in the study in the second year. Implementation during the second year was stronger but still did not achieve fidelity based on pre-specified fidelity thresholds. Analyses of teacher survey data revealed that the program had a statistically significant positive impact on teachers' enthusiasm about teaching and a marginally significant positive impact on teachers' self-efficacy at the end of the 2-year program. Nevertheless, the study did not find any significant impact on the quality of classroom interactions or student engagement based on observations at the end of Year 2 or on students' math or English language arts achievement at the end of Year 1. (Year 2 student achievement data are not yet available.) Results from this study need to be interpreted with caution given study limitations resulting largely from the influence of the pandemic. [American Institutes for Research (AIR) collaborated with Teachstone to implement this study.]