This monograph demonstrates how a teacher continuing professional development (CPD) programme effectively enhances English language teachers’ knowledge, beliefs, and classroom practices in formative assessment (FA). It introduces the "Pathway for Teacher CPD of AL", a practical framework offering direct guidance for teacher educators, researchers, and practitioners seeking to advance FA practice and literacy. The book makes distinctive empirical and theoretical contributions to FA research in language education, examining FA as an integrated process rather than isolated techniques. The study explores the full FA cycle—clarifying learning goals, eliciting and interpreting evidence, providing feedback and acting on it—providing a comprehensive account of effective implementation. It offers much-needed evidence on how enhanced teacher FA literacy improves student English achievement and supports self-regulated learning, clarifying the link between teacher development and student outcomes. Overall, the book advances a more nuanced and context-sensitive understanding of FA in real classroom environments. It is a valuable resource for researchers, teachers, teacher educators, and graduate students in applied linguistics, second language education and teacher education, among other disciplines.