This book presents a detailed account of a self-study in which the author considers why a developmental perspective matters in language learning within an intercultural orientation, and how teachers of languages might understand and attend to this notion in their work. The discussion is based on the author’s experience as a teacher-researcher and traces aspects of teachers’ work from planning, teaching and mediating, to assessing and judging evidence of student learning and development over time. This book is grounded in a praxis view of language teaching and learning and will be of interest to other language teachers, pre-service teachers, teacher trainers and applied linguists.