The assessment of children in their years before school and their first years of school has been, traditionally, informal. Further, assessment of children's mathematical skills at this level has been infrequent compared to social, emotional and physical assessments. However, there are contexts where reliable, valid, standardised data from assessment in mathematics are required. This paper outlines the development of two assessment tools for mathematics that were originally developed for such contexts. Item Response Theory (IRT) analyses enabled the construction of assessment forms that address the range of abilities of 4-to 8-year-old children, and provided the scales used for constructing formative and summative reports of achievement. A description of the development of the assessment tools and the IRT analysis that provides the reporting formats are presented together with some research uses of the tools.This article describes the development of two mathematics assessment tools suitable for use at the pre-school level, where formal assessment is rare. The article also describes how two issues in classroom assessment that challenge the development of assessment tools at this level were overcome. These issues are: the wide range of mathematical understandings of children of this early age; and the need to provide reporting to teachers that will assist in planning for appropriate mathematical learning experiences for the children assessed.The purposes of this article are: to demonstrate the possibilities for standardised assessment in the early years; to show how Item Response Theory (IRT) analyses can provide reporting formats for assisting early years professionals; and to describe some examples of two assessment tools in research contexts. While there are some necessary differences in the detail of these assessment tools, the development of one parallels the other. In some of the following sections both tools are described separately, and in other sections the tools are discussed together. When examples are used, the source assessment tool is indicated.