This academic work begins with a compact presentation of the general background to the study. The presentation provides readers who know little of the topic and of the structure of the educational system as well as of the value given to education in Nigeria with a clear picture. It concentrates on the dynamic interplay of the effect of academic and professional qualification and teachers' job performance in Nigeria. The aim of this study is to produce a systematic analysis and rich theoretical and empirical description of teachers and teaching competencies. The theoretical part comprises a comprehensive literature review that focuses on research conducted in the areas of academic certification and professional qualification and teachers' job, teaching competencies, and the role of teacher education with particular emphasis on school effectiveness and improvement. The empirical part involves describing and interpreting what educational objectives can be achieved with the help of teachers. The findings in this study reveal that teachers matter and as such they should be prepared adequately for the task ahead.