This paper provides an overview of assessment policy and practice in mathematics for early years classrooms in New Zealand between 1993 and the present day. It describes the introduction of school entry assessment for children starting school at age five. A numeracy initiative, the Numeracy Development Projects (NDP), for students in Years 1-10 was developed a decade ago out of a pilot project with Count Me In Too. Most recently, a consultation process was undertaken as part of introducing national standards in mathematics for students in Years 1-8. The paper also presents some data from assessments by teachers as part of the NDP initiative, showing the complex relationships between number knowledge and strategy for students in Years 1-4. The paper concludes by asking that individual diagnostic interviews to enable the provision of quality teaching continue to be supported as part of the introduction of national standards.