This book presents an in‐depth study of assessment innovation and its impact on teaching and learning. The context is New Zealand, and the focus is additional languages other than English and the recent introduction of a radical new assessment of students’ spoken proficiency, called interact. The book crosses the traditional theoretical and methodological boundaries associated with language testing research, which focuses on assessment performance, and presents an alternative approach where stakeholders become the centre of interest. It advances our understanding of how assessment innovation impacts on two key groups - teachers and students in schools - based on data collected from a substantial two‐year research project. It presents an account of these stakeholders’ perceptions of the validity and usefulness of the new assessment in comparison with the more traditional test that it has replaced. Assessing Foreign Language Students' Spoken Proficiency makes an outstanding and original contribution to the field of second and foreign language teaching, providing a theory and research-based account of the development of a learner-centred approach to oral proficiency assessment. It is an important resource for teachers and teacher educators as well as assessment and curriculum specialists worldwide. It deserves to be widely read.