The purpose of this study is to investigate the effects of the approaches to teaching and learning (ATL) of Language B, one of the subjects of the Diploma Programme offered by International Baccalaureate®.(IB) This study used a bibliographic survey to compare the study of English as a Foreign Language based on the ATL of the Japanese National Curriculum, and the one based on the ATL of Language B. To analyse the effects of the ATL of Language B, Academic Word List (Coxhead, 2007) and rubric designed by the IB was used as quantitative research. The participants used in the study were Japanese private high school students, and the experimental group was 82 students, the control group was 80 students. The result indicated that the experimental group increased their academic writing skills more than the control group. The effects of the ATL of Language B has actually not been revealed as of reporting, however this study succeeded in revealing that the ATL of Language B were effective for increasing English competency, which is required as one of the global competency skills.