This study attempted to discover the operative cultural assumptions that guide school people's solutions to external and internal problems and that are taught to new members as the correct way to approach these problems. Schein's (1984) levels of culture and their interaction formed the conceptual framework for the study. The research method was based on Schein's (1985a) Joint Exploration Through Iterative Interviewing methodology which involved a series of encounters and joint explorations between an outside investigator and various inside key informants. <p>This methodology incorporated a triangulation approach using data from interviews, observations, and archival material. Data were collected over a four-month period within one school nominated by central office personnel of the Westville Catholic Board of Education. Throughout the data collection phase, formulating hypotheses about the school's assumptions was used to guide data collection and analysis. Data were categorized based on Schein's methodology of using basic assumptions to form cultural paradigms. <p>Data concluded that three basic assumptions guided life at St. Gabriel School: (1) the Catholic faith and the Christian value system pervaded all school activity; (2) a transactional leadership style influenced decision-making, relationships, communications, and the teaching-learning situation; and (3) the student's social needs were emphasized at the expense of academic learning. Staff, students, and parents appeared to be socialized into all three assumptions. This study revealed that the principal had a major impact upon how all three assumptions arose and were maintained. The religious assumption was initiated as part of the principal's leadership role. His leadership style emphasized student's social needs and resulted from his espoused philosophy of learning. Teachers, parents, and students possessed the same basic assumptions. Each group contained individuals who espoused values different from those embedded in the three assumptions, but the predominant members representing each group were living out the assumptions. While some members in each group desired change, no one was able to effect change. The possibility of establishing a school culture which encompasses the school effectiveness characteristics within the context of these three basic cultural assumptions would be problematic. St. Gabriel School did not demonstrate a shared vision on academic learning were planned curriculum, high expectations, and ongoing assessment reflected school academic goals. Collaborative and transformational relations were not characteristic of the staff. <p>Schein's (1984) conceptual model, developed for the study of basic cultual assumptions, was useful in deciphering the culture of St. Gabriel. Schein's analysis of culture as existing at three different levels proved to be an important distinction as data were collected. His Joint Exploration Through Iterative Interviewing methodology enabled the underlying assumptions to be brought to the surface. Schein provided a valuable theoretical framework and an appropriate methodology for studying the deepest level of an organization, that is, its cultural assumption. Judgements and conclusions about schools can be made on superficial levels of observation. In order to truly understand the functioning of any school probing beneath these source levels is necessary. This study confirmed that, for this instance, principals have a dominant influence on the culture of schools, therefore, they should be helped to use a cultural lens in order to understand and assess the state of effectiveness of their schools. Finally, a number of theoretical, methodological, and practical implications were noted.