Although different studies have been conducted regarding Education for International Understanding, few studies have explored the feature and issues on Education for International Understanding with a form of High Cluster programme. In this regard, this study attempted to analyze practice and issues of the Education for International Understanding in A-high school in Gyeonggi-do. The authors of this paper have participated with developing the programme and teaching for three years in person. Major findings revealed four issues; First, the high school students’ passive attitude and mundane fatigue prohibited their in-depth learning of international affairs and its contents. Second, due to heavy pressure of academic achievement for the preparation of university entrance exam, Education for International Understanding are positioned within marginal sector in Korean high schools, which increase instructor s teaching load in order to encourage their active participation. Third, absence of diverse evaluation framework would produce confusion of outcome of Education for International Understanding in the high school. Finally, lack of support for instructors can cause low quality of education programmes.