Teachers make decisions every lesson based on what they think students understand. However, without reliable ways to check understanding, teachers risk teaching to an illusion, and those most likely to be left behind are often the most vulnerable. What Are They Thinking? tackles one of the most consequential questions in teaching: how can we reliably find out what students actually understand, and use that insight to decide what to do next?The book explores the research behind checking for understanding and shows why it is central to so much of what we know about how learning happens. Drawing on evidence from cognitive science and formative assessment, it provides practical guidance to help teachers design checks that include every student, reveal misconceptions early, and allow teachers to respond thoughtfully to the evidence they provide. Examining checking for understanding across key areas of teaching and learning, the chapters cover:? Prior knowledge, including schema theory, meaning-making, and consolidation;? The science of learning, including desirable difficulties, learning versus performance, and assessment;? Practical classroom techniques, such as cold calling, mini whiteboards, hinge; questions, and exit tickets applicable from early years education to post-16 and beyond? Applying checks for understanding in SEND, adaptive teaching and oracy. Part of the Teacher CPD Academy series from InnerDrive, What Are They Thinking? is essential reading for teachers and school leaders who want to move beyond reassurance, make learning visible, and teach with greater precision, confidence, and impact. Checking for understanding is framed as a moral and professional imperative, making it more likely that teaching is guided by evidence rather than well-intentioned intuition.