Competent teachers are the most critical piece in improving students’ achievement and closing the achievement gap. The single most important influence on student learning is the quality of teaching, yet most schools don’t define what good teaching is (Danielson, 2006). This is a problem because if it is not defined, teachers may not be given the opportunities to improve practices in the classroom, which invariably may affect student’s achievement negatively. This study assesses teachers’ competence in secondary school; examines the factors influencing teachers’ competence, investigates the student perceptions of teacher leadership style and how these perceptions affect students’ academic performance. Four selected secondary schools in Ikeja Local Government Area of Lagos State were used as case study. One hundred students were randomly selected from these schools. Four hypotheses were developed to test the correlation between teachers’ competence and academic performance of students in secondary school. The research contends that teachers should not be left alone in the education process of secondary school students and should be retrained to meet up with the evolving trends in education.