In 2004, all accredited public schools in Iowa enacted a research-based program to increase student achievement. The Iowa Professional Development Model has outlined a sequence of steps that those in schools should follow. The purpose of this qualitative case study was to discover and understand the behaviors and practices of one school principal in a high-implementation school as he worked with a staff using the Model. Understanding how a principal led staff as the Model was implemented should help to inform others regarding the development of capacity and new knowledge and skills that are needed by those in schools.;Data were collected that related to the behaviors and practices demonstrated by the principal during implementation of the Model. Data included observations of professional development sessions, leadership team meetings, principal interviews, document analysis, and field notes.;In this dissertation, the IPD Model was the process used to first code the principal's actions and behaviors. Leadership responsibilities were further defined through the Mid-continent Research for Education and Learning (McREL) meta-analysis research study, as all 21 principal responsibilities have been identified as unique behaviors that represent important knowledge, skills, and practices for principals to emphasize to positively impact student achievement.;This study found there were 16 specific practices and key factors enacted by the leader which contributed to the teachers' implementation of research-based practices and professional development. A principal needs to be able to help colleagues understand how school improvement can be integrated into the building and provide the supports necessary.;As the research was conducted to gather data on the principal's behaviors and practices, additional data were revealed that showed the IPD Model and McREL research do not encompass all of the issues with which school leaders contend. These issues generally cannot be addressed solely by the principal, but rather are systemic issues that require collective efforts.;Professional learning that results in student achievement is challenging for those who view school improvement as an externally initiated reform. Implementation of the Model can be done effectively when the principal plays a key role; however, it requires highly effective leadership.