This study evaluates aspects related to P12 principals' professional development needs in South Carolina regarding the three domains of school leadership: management, instructional leadership, and program administration. A survey to rate principals' current leadership knowledge, rank order their professional development needs, and provide a confidence rating regarding their abilities was given to over 1,100 principals and 85 superintendents. Through examining relationships with a psychometric model, results derived latent leadership ability scores and self-reported confidence ratings of principals as well as the superintendents' leadership scores and confidence ratings of their principals. This study found a significant discrepancy between principals' and superintendents' confidence ratings and their corresponding leadership ability scores, respectively. A further analysis of the rank-ordered professional development needs highlighted instructional leadership to be the most needed topic for professional development. Finally, atypical response patterns regarding principal's current leadership knowledge are also identified through person-fit analysis to provide additional information regarding P-12 principals' professional development needs.