Teachers are the pillars of the development of society’s building blocks i.e., the students, so for the effective and constructive nourishment of the students, the performance of the teachers should be excellent with the assistance of external factors. So, to empirically evaluate the teachers’ performance, this study used a quantitative research methodology and elucidated the influence of school environment, character development and school management on teachers’ performance level with the mediation of individual personality factor of efficacy. The study targeted the teachers of high schools serving in Indonesia and collected data purposively using the survey tool and used a total of 227 valid and effective responses for results compilation. The analysis revealed significant results for all direct relationships and mediation was supported for the school environment and teachers’ performance. The study contributed a novel piece of evidence to the literature by enlightening the influence of external environmental factors at the school level on teachers’ performance.