Using various official sources, the article explores competing conceptions of the 'under- achieving ' school which have been operationalised in recent years. It suggests that there have been multiple, potentially conflicting definitions in policy discourse to which recent innovations have merely added a further layer of complexity. Using a simple conceptual framework comparing judgements made within 'standards' and 'progress' frameworks for evaluating schools' performance, it highlights the very limited range of conditions where judgements made within one tradition would complement those (...) made within the other. As the educational system begins to turn increasingly to use of so-called 'value-added' approaches as a way forward, the implications of these analyses for policy development, particularly in relation to the alleviation of social and educational disadvantage, are considered. (shrink)