This study presents how a professional development program (PD) of K-12 teachers affects participants' use of the earth system approach and their perceptions of using the urban environment for their science teaching and lesson unit development. This study utilized mixed methods to collect and analyze the data. Eleven urban teachers' pre-post lessons (45 lessons) were analyzed quantitatively using a lesson plan analysis tool, modified by the author, and their lesson reflections were analyzed qualitatively. The findings of this study show that the PD program influences the teachers to choose more topics and content knowledge based on the earth system approach and to assess the topics and content knowledge with more appropriate methods. Specifically, the teachers use more urban environmental factors/topics in their post lesson to teach the environmental topics of urban area. However, according to the statistical analysis of pre-and postlesson plan scores, the accuracy of the earth system knowledge that participants used in their lessons did not change significantly (p〈0.05) (Table 4), which means that the PD program did not affect the improvement of the teacher's content knowledge in earth system science. Implications of this study are discussed.

• Nam, Youn-Kyeong(Department of Curriculum and Instruction, University of Minnesota)