This article focuses upon the Japanese government's decision in 2009 to direct an 'English-only' strategy for English language education in senior high schools from 2013. In the "Course of Study 2009," and more recently again in the "Course of Study 2018," the Japanese government implicitly blames the local grammar-translation method of teaching, known as "yakudoku," for the failure of teachers to foster their students' English proficiency, and suggests that it should be replaced 'in principle' by English-only classes. This article examines how the policy originated and was then formulated in the "Course of Study 2009," and how local teachers received it. In order to investigate stakeholders' perspectives regarding the use of "yakudoku" and its replacement by an instrumentalist strategy, a three-month discourse-oriented ethnographic field study was conducted in Japan. The data were then scrutinised using a critical discourse analysis methodological framework [Fairclough, N. (1992). "Discourse and social change." Cambridge: Polity Press; (2003). "Analysing discourse: Textual analysis for social research." London: Routledge]. This article makes the argument that the term "yakudoku" has been manipulated by the Japanese government for the purposes of marginalising the use of Japanese in the classroom and of instituting its preference for a western-centric model of learning for the teaching of English in schools.