The results of the National Assessment of Educational Achievement (NAEA) from 2010 to 2013 have shown a downward trend in ninth graders’ science average achievement scores from 2011 to 2013. In particular, the percentage of students in the Advanced level decreased dramatically from 19.95% in 2010 to 11.48% in 2013, while the percentage of students in the Basic level showed an increase. Also, several statistics were analyzed, such as the percentage of correct answers, item discrimination, and average response rate by achievement level, for 128 items. As a result, we were able to identify possible discrepancies between students’ academic abilities and their respective curriculums. In addition, through the results of the Science Achievement Assessment, the characteristics of each level of student achievement can be defined so that we can help students, teachers, and schools by providing them with basic information. The characteristics of each achievement level were based on the analysis of the cognitive characteristics of representative items. We also included discussions on how to fine tune the achievement standards of the science curriculum as well as how to implement improved and customized teaching and learning methods.