“Disciplinarity” and “interdisciplinarity” have become keywords for knowledge and education in the twenty-first century. This development requires that administrators, curriculum planners, and teachers at all levels of the educational system have a common understanding of both terms and their relationship. The primary case study is the school level in the United States. Yet, comparisons with other nations suggest a platform for longer-term international dialogue that bridges the discourses of interdisciplinarity across national contexts as well as school and university levels. A shared discourse and programs of teacher training require awareness of historical contexts of interdisciplinary education, major terminology for distinguishing design models, characteristic pedagogical approaches, and related learning skills.