The purpose of this study was to investigate the teacher related factors affecting student achievement in Biological sciences in selected secondary schools in Bomet and Kericho Counties. In order to achieve the purpose of this study, five specific research objectives were generated to guide the investigation i.e. to assess the relationship between the teachers gender and students achievement in biological sciences, to assess the relationship between teacher experience and student achievement in biological sciences, to determine the effect of the teachers knowledge levels on students...