Besides teachers knowledge of subject matter, their proficiency in pedagogical content knowledge (PCK) is a strong determinant of what student can and do learn.This study sought to establish teachers' proficiency level in mathematical knowledge for teaching (MKfT) by examining teachers' interpretations of students' problem solving strategies. A sample of Kenyan high school mathematics teachers participated in the study whose central thesis was that, effective learning of mathematics depended on teachers' level of proficiency in PCK. Study instruments included questionnaires, classroom...