Abstract
This research paper examines the professional and non-professional methodological competencies of secondary school teachers in Nigeria. The main focus of this study is to probe the impact of professional and non-professional methodological competencies as a predictor of teaching effectiveness. Although this exploration is survey research, a questionnaire was used for data gathering, and multiple statistical procedures were employed in the analysis. This study contributes to the field both in terms of theory and practice. Theoretically, it provides an outline of school effectiveness and quality improvement that can be used as a basis for further research. The study identifies factors that create barriers to methodological competencies for the two categories of teachers used in this study. It also describes the present situation on the ground in Nigerian secondary schools. At the practical level, this outline might guide school leaders, education planners and policy makers in their school effectiveness and quality improvement endeavors.