The role and responsibilities of a principal as leader of a learning community within K-12 schools is undergoing dynamic evolution. This exploratory study describes and analyzes the professional growth of 18 educational practitioners while participating in a principal preparation cohort program. The study goal was to understand the nature of changes and the processes through which they occurred, and to link participants' professional growth to their readiness to assume school leadership positions. Researcher propositions guided the design and focus of this mixed-methods yearlong case study. Although the inquiry explores the preparation of educational leaders within a unique cohort of a university-based licensure program, the research was not intended to evaluate a particular program of principal preparation. Five themes emerged from the data that have implications for the preparation of new school leaders: (1) career aspirations; (2) leadership development; (3) role conceptualization into the principalship; (4) socialization into the community of practice; and (5) learning in cohorts. Experiential learning must be the core element of principal preparation to ensure needed skill development and socialization into the community practice. Career counseling is needed for aspiring principals, especially for women, to assist teachers as they make the transition from classrooms to administrative offices. (Contains 73 references.) (Author/RT)