How and why meaningful curriculum or program changes happen in physical education is important, but not well understood, especially at the secondary school level. In this longitudinal case study, we examined teacher-initiated changes in a high school physical education program. Data were collected through prolonged engagement over 5 years and included interviews with teachers and students, documents from the physical education department, field notes, survey responses, and presentation notes. A broad range of change forces, including a standards-based assessment program, was assessed using qualitative methods. Consistencies and inconsistencies between Fullan's theoretical framework on changes in education and what occurred in this physical education program are identified. Ways that change was aligned with Fullan's phases of change (Initiation, Implementation, and Institutionalization) were also considered. Results suggest that aspects of Fullan's framework are aligned with systematic changes in physical education. Teachers, as passionate, committed change agents, were essential for positive change. Elements of bottom-up and top-down educational reform were present in varying degrees. The effect of external change agents and funding, however, was noticeably absent.