Andrew Wrenn describes his work with Barry Williams and the teachers of the history department at Ailwyn School (11-14 comprehensive), Ramsey in Cambridgeshire. Devoting equal attention to the "what" and the "how" of history assessment, he shows how this group of teachers developed a fresh approach to assessment out of the collaborative planning of one new enquiry. A key characteristic of this department's use of "assessment for learning" is a concern to help pupils reflect on their own learning and to discover the value of doing so. Through a varied and integrated mixture of self-assessment, peer-assessment and teacher assessment, these pupils were helped to engage with a complex historical problem, discovering its wider historical significance and placing themselves at the centre of a judgement-forming process. A task-specific mark scheme plays a small part in a wide range of data that is useful to the teachers but the pupils receive no marks, grades or levels of any kind. Instead, the teachers engage deeply with ways of helping pupils to understand what it means to think historically. They use assessment to help pupils track the way that their thinking is changing and to set out the road to improvement in a way that is clear and, above all, motivating. [A combined list of references and notes is provided.]