This study aims to determine the analysis of the influence of principals' leadership, teacher professionalism, and work motivation on the performance of high school teachers throughout Ende Regency. This study uses quantitative methods. Determination of the sample using the Proportional Random Sampling technique so that the research sample obtained is 246 respondents. Data collection techniques used are questionnaires and interviews. The data analysis method used is ordinary least square linear regression using the SPSS program. The results of the study prove that the results of this study support the results of research which concludes that teacher professionalism has a significant positive effect on teacher performance. The results of this study also support the results of research which states that the better the professionalism of teachers, the more it affects teacher performance positively and significantly. Thus, and vice versa, the worse the professionalism of teachers, the lower the performance of high school teachers throughout Ende Regency. The principal pays attention to the teacher's performance, namely to be more professional and work motivation to the teacher's performance.