Nigerian secondary schools are faced with problem of supervisions. In this study, the aim is to assess the general roles of school supervisors in improving teaching quality and effectiveness of schools supervisions. Actually the study intends to make a review on some issues related to supervision in Nigerian context, emphasizing professional profiles and roles in educational system, specifically in quality improvement of secondary schools and also highlighting the concepts of supervision, differences between supervision and inspection, quality assurance/ quality management as well as quality in teaching and learning. Therefore, it suggested that supervisors as catalysts should facilitate the implementation of the various sets of roles which will improve the teaching-learning situation in the input-process. this is geared towards an effective, viable, vibrant and qualitative educational system. Hence, the supervisor must seek for genuine cooperation and concern, positive and acceptable disposition among the teachers and their subordinates.