The goal of this study was to determine how one school district’s Principal Pipeline Program supported aspiring leaders in their journey towards effective school leadership. Using a convergent design, the researcher utilized teacher perception surveys, administrator evaluation data, and focus group feedback from the aspiring leaders to measure program impact. Program elements included pre-service leadership training, a full-year internship as a building-based assistant principal, and context-based mentoring from school principals. Results indicated that by the end of the internship year, Pipeliners were statistically similar to assistant principals in their leadership behaviors as perceived by teachers and also in their evaluation outcomes observed by supervisors. Implications and suggestions for future research in aspiring school-leader development have been included.