This book explains the origins of underachievement, both overt and covert, especially in more able learners. It provides a model that identifies a range of external and internal factors that work in concert to lower achievement. Formal tests identify some underachievers but more than two thirds remain unidentified and other strategies are needed, in particular cognitive-based curriculum challenge and performance-based realistic assessment. 'UAch' may also be masked by learning disabilities and socioemotional and behavioural difficulties. All of these can form barriers to learning that can be overcome with appropriate teaching and learning strategies. These problems and relevant strategies for intervention are explained in the book. Research underpinning identification, intervention and remediation is detailed - including recent research by the main author to show the current nature and range of the problems in ordinary schools. The final chapters contain case material from schools that have been proved successful in lifting underachievement and shows how they have succeeded.This is entirely new material based upon research undertaken for NACE/London Gifted and Talented by Belle Wallace and the editor/author.