The research objectives were; 1. To learn the working performance of the principal at SD Muhammadiyah Kulon Progo, 2. To learn the quality of school at SD Muhammadiyah Kulon Progo. 3. To learn the effect of principal’s working performance toward school quality. The school is SD Muhamadiyah Kulon Progo. The subject of the research was the principal and the teachers. The data were collected through questionnaire, documentation, and observation. The research used Simple Linier Regression to calculate the effect of the principal’s performance on school quality. Based on the research, it can be concluded that; 1. The working performance of SD Muhammadiyah Kulon Progo principal is categorized as very good. 2. The quality of SD Muhammadiyah Kulon Progo is very good. 3. How much influence principal’s working performance and the quality of SD Muhammadiyah Kulon Progo. Key words: principal’s working performance, school quality