Abstract-Pedagogic Content Knowledge (PCK) is veryimportant for teachers because it shows teacher understanding of science knowledge and pedagogical knowledge. PCK covers the knowledge of content and pedagogy such as teaching knowledge (the subject knowledge and their belief in that, and how to teach it), curriculum knowledge (what and when to teach), assessment knowledge (why, what, and how to assess), the knowledge of students' comprehension toward the subject, and instructional knowledge. To assess teacher PCK we used an instrument called content representation (CoRe).Although CoRe has shown effectiveness in assesssing teacher PCK, however, it does not include reasoning. Learning is considered meaningful when learning activities involve student' to think and to reason. Thus, we need an instrument which enables us to assess teacher's PCK about reasoning and students' reasoning skill. Therefore, for the purpose of the study the researchers modified CoRe to include reasoning. Samples of this study are 8 teachers and 42 students. The modified CoRe measured teacher's formulation of learning goals, content to be taught, pedagogical aspects in teaching particular material, assessment of students learning, and the methods in developing students' reasoning skill. Based on their responses to CoRe, teacher PCK are classified into pre PCK, growing PCK, and maturing PCK. Paper and pencil tests are administered to students to measure their reasoning skills. The instruments consist of thwelve questions related to pollution, i.e. water pollution, air pollution, and land pollution.