Korea is preparing to introduce a high school credit system in 2025. The purpose of this study was to analyze the characteristics of IBDP’s elective subjects related to first language as a competency-oriented curriculum and to derive implications for the composition of elective subjects in Korea’s high school credit system. The first characteristic of IBDP is that although there are differences in the subject text and background knowledge, the first language-related elective subjects share the goals of the subjects and the evaluation model, with a focus on enhancing the learner’s communication capability and knowledge-based exploration capability. The second characteristic of IBDP is that each first language-related subject provides competency-based assessment tasks asking students to select relevant knowledge and skills and solve the given or self-created questions. Based on this analysis, this study provides four implications for Korea’s high school grading system: “specification of the competencies required in the high school curriculum,” “constructing elective subjects in terms of competencies,” “concretizing the competency-based evaluation method in the elective subjects,” and “considering the choice of students’ self-directed exploration in the elective subjects.”