This paper provides information on a measure that was developed to assess children's level of development at preschool and entry to school level, as well as their readiness for formal schooling. This measure--"Who Am I?"--is based on early copying and writing skills and is designed to identify the broad stages of development that underlie children's readiness for more formal learning in a school situation. Although originally developed in Australia, it has now been used in studies in a number of different countries, including Canada, and data from these studies provide some insight into the variations in development that are associated with different patterns of preschool provision and different ages of entry into an educational program. The results of these studies indicate that "Who Am I?" provides a valid measure of development across different language and cultural groups and can therefore be used as a tool to evaluate the effectiveness of different forms of early childhood provision, as well as children's readiness for more formal learning in a school situation. (Contains 14 tables, 2 figures, and 5 notes.)