Classroom assessment practices are greatly influenced by national and local policies on assessment. Typically, these include accountability requirements for schools to evidence and report their students' learning in the form of specific learning outcomes, calibrated against national benchmark standards of achievement and progression. An implication for teachers is that their understanding of children's learning is influenced by an official curriculum that is more likely to be weighted towards particular policy priorities, and desired learning outcomes. This means the knowledge, skills and understanding that children develop outside school are less likely to be included in classroom assessment measures or judgments about desirable progress and achievement. This article explores what happens to teachers' thinking when they learn about their children's informal learning "outside school" and begin to relate to learners in a different way. The findings reported here from a New Zealand three-year longitudinal study identified possibilities for teachers to assess expanded conceptions of children's learning within the classroom, even though the pressures of assessment against National Standards were ever present. We argue that teachers engaging with knowledge of their students' informal learning act as a catalyst to rethink and re-conceptualise learning more broadly. Incorporating a strong student voice component in assessment, together with a focus on ipsative assessment, enables teachers to mitigate some of the unintended educational consequences of assessment accountability policies and practices.