This study aims to explore ways to improve the elective-centered curriculum in the 2015 Revised National English Curriculum. To do so, first, the study analyzed the appropriateness of electives in terms of differentiation. Newly introduced in the curriculum, career-related electives were not clearly defined regarding topic, achievement standards, and level. Second, to investigate the current status of course completion, the study analyzed the number of elective courses which were mainly selected and identified which courses were highly utilized and its reasons. The results showed that out of the eight elective courses offered by the curriculum, general electives were mainly selected at schools. It was also found that career-related electives were not differentiated clearly enough, which caused difficulties in teaching and evaluation. Finally, considering the purpose of the high school credit system, which strengthens students’ rights to choose subjects according to their career paths, level, and interests, it would be necessary to secure the differentiation of subjects and to systematize course completion to establish clear guidelines for course selection.