The effectiveness of instructional supervision of heads of school to improve the teaching and learning performance has been questioned by various studies. This study investigated the instructional supervision role of heads of school and its influence on teachers’ work performance in public secondary schools in Lindi region, Tanzania. The study examined the extent to which heads of school discharged their instructional supervisory responsibilities and assessed the extent to which heads of school instructional supervisory activities influenced teachers work performance. The study was informed by mixed methods approach with a sample of 57 public secondary schools out of 124 public secondary schools found in the region. 171 respondents were included in the study including 103 teachers, 57 head masters and 11 class masters. The study used questionnaires; interviews and documents review as tools for data collection. Thematic analysis was used for the qualitative data, while for quantitative data, descriptive and inferential statistics were employed. The study revealed that despite the challenges that heads of school demonstrated a significant understanding of their supervisory instructional duties, but did not effectively engage teachers in improving professional skills. The analysis showed that teachers seemed to avoid conflicts with head teachers and hence limited mechanisms to improve performances. Keywords: Effective teaching, School leadership, Supervisory skills. DOI: 10.7176/JEP/13-14-01 Publication date: May 31 st 2022