The power of assessment for learning: Twenty years of research and practice in UK and US classrooms, by Christine A. Harrison and Margaret Heritage, Sage, 2019, 144 pp.,

Ever since the seminal work of Inside the Black Box by Black and Wiliam was published in 1998, researchers in the educational testing community have had a growing interest in Assessment for Learning (AfL).Differing from the traditional summative assessment, AfL offers an alternative perspective towards assessment, focusing on improving students' learning through teacher-student interactions, involvement of students in the process of assessment, and provision of constructive feedback.Similar theoretical conceptulisation of AfL appears in the frameworks of LOA (Carless, 2007; Jones & Saville, 2016; Turner & Purpura, 2016) and formative assessment (Black & Wiliam, 2009).Although AfL, LOA, and formative assessment have simulated heated discussions in the assessment community, the practical implementation of AfL has not been satisfactory and at times failed to live up to key stakeholders' expectations.Against this backdrop, The power of assessment for learning: Twenty years of research and practice in UK and US classrooms by Margaret Heritage and Christine Harrison is a timely volume that could provide stakeholders with practical examples and guidance for implementing AfL in genuine teaching and learning contexts.The book, which has six chapters in total, sets the scene in the UK and US.It first brings attention to AfL (Chapter 1), then discusses and compares key AfL practices in two countries (Chapter 2), explains the key principles of AfL with substantial evidence (Chapters 3, 4, and 5), and concludes with future research directions for advancing AfL (Chapter 6).Chapter 1 revisits the key ideas in Inside the Black Box and the concept of AfL to explain when and how AfL originated in the UK and the US.It starts a rich discussion on AfL by first defining it.According to the authors, "AfL is a range of practices that encourages both teachers and learners to seek evidence of the ways in which students are developing their knowledge, skills, and understanding with the intention of using the evidence to