In this study, we investigated how elementary science teaching has changed with the introduction of the National Assessment of Educational Achievement (NAEA). Teachers are held accountable for student performance as measured by the mandatory nation-wide standards tests to satisfy the needs of accountability and quality assurance systems. In relation to the teaching of science in the elementary school, professionalism meets potential threats with the advent of national test. Through analysis of the classroom teaching and open-ended interviews, we explored the teacher's concerns about the national test and how their science classes have changed to prepare for this test. According to the results, the national test made elementary teachers accountable for the content of their science classes, limits teachers' autonomy in reconstruction of curriculum, and forced teachers to conduct conclusion-centered lessons even in elementary science classes. In addition, teachers argue that the national test precludes the possibility of differentiated education and differentiated assessment. Based on the results, we suggested a new professionalism in this accountability era, so called 'informed professionalism', which refers to the ability of teachers to interpret and implement curriculum and policy mandates at the local, school and classroom level to generate equitable and improved student outcomes through teaching and learning. We also suggested further research on the teacher professionalism in teaching science contents.