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The purpose of this study was to develop a conceptual model for the competence of high school principals in Tehran province. This qualitative research was carried out using a strategy based on the grounded theory. In this regard, using a targeted approach and theoretical saturation criterion, semi-structured interviews with 17 people (7 faculty members specialized in the field of educational management, 5 educational staff managers in Tehran province and 5 school principals) was applied. To obtain validity and reliability of the data, two methods of reviewing participants and non-participant experts were used. The results of the data analysis in three stages, open coding, theoretical coding and selective coding, represent 17 general categories. This paper analyzed the findings of the study in the paradigmatic model including: causal conditions ( the need for continuous improvement, material and spiritual support (Incentives), changes in knowledge and occupation), the main phenomenon (required knowledge, attitudes, and skills), strategies (development centers , providing direct training, implicit training (experimental), context ( collaborative work , supportive atmosphere, decentralized structure), intervening conditions (policy, rules and regulations of facilitator / barrier) and outcomes (improvement of learning quality, organizational development, professional development).