This study examines what aspiring principal candidates in one university-based preparation program learned as a result of developing and implementing a school improvement plan. A case study approach was used to examine 53 aspiring principals' reports of what they learned from implementing school improvement plans. Findings revealed three significant themes: (1) the importance of collaboratively engaging the participants of the school improvement plan; (2) the essential need of establishing relationships; and (3) understanding the significance and impact of data-driven decisions. Findings can inform leadership preparation programs to redirect coursework that will help aspiring principals improve leadership skills.