The study explores how school principals transition from following rules to practical skills when they get promoted. Researchers interviewed participants and used a method called framework analysis. They found that becoming a principal in Korea is seen more as achieving rule-based professionalism than practical skills. After promotion, principals develop practical skills related to their experience. To support this transition, it is suggested to provide more help to reduce the gap between rule-based and practical professionalism, recognize principals as diverse individuals, and establish standards for practical skills.