Adults with low skills in language, literacy and numeracy (LLN) are numerous in many OECD countries. They can include early school leavers, older learners who have not used their skills over time, immigrant and refugee learners, or individuals with disabilities. The consequences of these low foundation skills span the economic, health and social well-being of individuals, families and communities. Investment in this sector of adult education is therefore crucial. But what is known about whether and how programmes are meeting the needs of diverse learners? This study looks specifically inside the programmes for adult LLN learners, with a focus on formative assessment - referring to the frequent assessment of learner understanding and progress to identify needs and shape teaching and learning. Drawing upon evidence gathered in country reports, exemplary case studies and international literature reviews, it examines the impact and implementation of different teaching, learning and assessment practices for adult LLN learners; the way innovative programmes address the very diverse needs and goals of this population; and the policies that support or hinder effective practice. This book provides a strong foundation for understanding the fundamental issues at stake in the adult LLN education, and can guide future policy, practice and research. It will be of particular interest to policy makers, teachers and instructors, researchers, and students. A companion report which studies formative assessment in lower secondary schools was published in 2005 under the title Formative Assessment: Improving Learning in Secondary Classrooms.