This study is a report of the collaborative action research which has been conducted between a Korean earth science teacher and science education researcher. A two-year long action research effort was made in order to improve the teacher’s earth science classrooms in pursuit of constructivist principles of learning. The process of the action research was described with the aim of increasing the awareness of science teachers and science education researchers regarding action research. Quantitative evidence was presented to indicate the effectiveness of the collaborative action research in creating constructivist learning environments in the classrooms. The process and quantitative evidence from the action research permitted a consideration of implications for future efforts to improve science classrooms.