The aim of this study was to design and present a model of leadership styles for high school principals. The main pillar of growth and development of any society is the skilled and specialized human resources in that society, and education plays a very important role in nurturing the next generation. This research is applied in terms of purpose, using an exploratory mixed methods approach. In the qualitative phase of research, a semi-structured interview and a focus group were used to collect the data. In the quantitative phase of research, a questionnaire was used based on descriptive analysis and inference. The statistical population of the study included all experts in the field of educational management as well as school principals and management planners in schools. The sample size of the research based on Cochran's formula was 480 principals and teachers and 20 faculty members, and a validation questionnaire of 74 questions (135 people). The validity of the researcher-made questionnaire was confirmed by experts, and the reliability of the questionnaires based on Cronbach's alpha was calculated to be (0.85) and (0.97), respectively. Analysis of research data in the qualitative phase involved thematic content analysis method using interview coding by MAXQDA software, and in a quantitative phase, data analysis was done by SPSS and SmartPLS. The results showed that school principals' leadership styles included 13 elements, which were confirmed after presenting the model and examining the effect size and correlation of all variables. Finally, the necessary measures can be taken according to the proposed model.