The main objective of this study was to investigate the effect of excellence-oriented leadership on the improvement of educational standards with the mediating role of organizational culture in upper secondary schools in Mahabad County. This research is applied in terms of purpose and descriptive–correlational in terms of methodology, conducted within the framework of structural equation modeling (SEM). The statistical population included all upper secondary school teachers in Mahabad, totaling 645 individuals identified through the local education authority. The sample size was determined using Cochran’s formula, resulting in 240 participants selected through simple random sampling. Data were collected using three standardized questionnaires: the Educational Standards Improvement Questionnaire (Kobraei & Roodbari, 2005), the Denison Organizational Culture Questionnaire (Denison, 2006), and the Excellence Leadership Questionnaire developed by Bass and Avolio (2006). Data analysis was performed using structural equation modeling with Smart-PLS4 and SPSS version 30 software. The results indicated that excellence-oriented leadership has a positive and significant effect on improving educational standards. This effect was also confirmed indirectly through organizational culture (t > 1.96, p < 0.05, and zero not included in the confidence interval). Overall, the findings suggest that organizational culture plays a significant mediating role in strengthening the impact of excellence-oriented leadership on educational quality. Therefore, enhancing organizational culture in schools can facilitate the effectiveness of excellence-oriented leadership in improving educational standards.