This study aims to investigate empirically how well primary school principals perform core competence, as perceived by the teachers of the school, and what aspect of core competency is thought to be important and necessary in managing the principalship, particularly in the times of rapid change when principals are destined to face a variety of challenges. To serve the purpose, a questionnaire survey was conducted onto a group of 400 elementary school teachers in Gyong-gi province who were selected on a random sampling technique. The analysis of the data, employing the SPSSWIN statistical program which includes t, F, and Scheff? tests, has confirmed the following observations. First, relatively high is the degree to which teachers perceive the level of the core competency performed by the principals, especially in such competency areas as the administrative and financial management, the management of the school vision and objectives, and the relation with the parents and the community. Second, relatively high is the degree to which teachers expected the level of the core competency to be performed by the principals, especially in such competency areas as the administrative and financial management, the organizational and personnel management, the management of the school vision and objectives, the development of the expertise of the teaching faculty. Third, relatively high is the degree to which teachers feel the gap between the perceived level of performance and the expected level of performance, especially in such competency areas as the change management in the school organization, the development of the expertise of the teaching faculty, the development of the curriculum together with teaching and learning.