The purpose of this study was to investigate the difference of teachers` interaction with their students when teaching science in New York (NY) and in Korea. As part of the 2011 Korean International Teacher Fellows (KITF), supported by the Ministry of Education, Science and Technology (MEST) and the National Institute for International Education Development (NIIED), Korean science teachers observed, for six months, New York`s science classes in terms of how teachers interact with their students and how students learn science during science instruction. The participants were 10 science teachers in five middle and high schools that taught Physics, Chemistry, Biology, Earth Science, and Environment Science in NY. The National Board for Professional Teaching Standards (NBPTS, 2003) and Instruction as Interaction (Cohen et al., 2003) were used as an instrument to identify each teacher`s teaching and classroom interaction. Several characteristics of science classes in NY were revealed, which are different from Korean science classes. First, science teachers in NY dominantly put more focus on their subject of teaching during science interaction while, Korean science teachers not only teach science but also do counseling to students as a homeroom teacher. Second, science teachers in NY acknowledged the students` individuality and have positive experiences of professional development supported by their school and district more than Korean science teachers do. Third, science teachers in NY sometimes showed limited knowledge about the concepts of science and lack of collaboration with other science teachers. This characteristics may prevent the school from strengthening its subject program and keeping equity across the grade levels and courses.