Children can sometimes appear to understand a concept such as place value without really having a deep understanding. Judy Bailey stresses the importance of listening carefully to children to identify their current understandings and then building on them systematically, using a range of materials, to promote a deep conceptual understanding. This article reports on the collaboration of the author (a university mathematics educator) and a relatively new classroom teacher. The teacher sought to address the needs of a group of lower-achieving seven- and eight-year-old children within the regular class mathematics programme of a large urban primary school. This small study was part of a two-year project focused on raising school-wide achievement in mathematics in the school.