The purpose of this study is to diagnose the current states and the problems of student assessment of the differentiated curricula at the elementary school. For that purpose, this study had the focus-group interviews and conducted a survey. The survey items that were developed through focus-group interviews consisted of the four main parts: questions about the level courses, the enriched?supplementary courses, the special supplementary courses, and the support systems. The results of this study are as the follow: First, in the level courses assessment such as mathematics assessment, teachers depended heavily on a paper-and-pencil test, performance assessment and differentiated test were not adapted fully. Second, in the enriched?supplementary courses, elementary school teachers perceived that the evaluation in general includes the contents of the enriched?supplementary courses as well as those of the basic courses, and that the formative evaluation is usually used for classifying the level. The feedbacks for all students were the most in the class. Third, in selecting the students for the special supplementary courses, both criterion-referenced assessment and norm-referenced assessment were considered. After finishing the special supplementary courses, additional tests were usually taken. A follow-up guidances were the most through the classroom teachers' individual guidances. Finally, teachers perceived that they do not have enough training related to student assessment in a differentiated curricula and that they want to have trainings about the various types of performance assessment and the feedback methods and then item building methods.