There has, in recent years, been a reemergence of interest in the early years and a renewed emphasis on the importance of early education programs to ensure that all children start school ready to learn. At the same time, the move toward evidence-based policy development has led to the need to demonstrate the effectiveness of early education programs in terms of measured outcomes. Questions have also been raised with regard to the effectiveness of different types of programs and approaches, and the age at which such programs should be introduced. In order to evaluate the outcomes of early education programs, it is necessary to have a measure that can assess the impact of programs in terms of the development of the underlying skills that are associated with subsequent learning and achievement at school. 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, "Who Am I?" has now been used in studies in a number of different countries, including Canada. 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 reported in this paper indicate variations in the patterns of development of young children according to both age and schooling. Development of early copying and writing skills is accelerated in cases where children enter preschool at an early age and are exposed to formal teaching of early reading and writing skills, as in Hong Kong. However, less formal preschool programs and later entry to school, as in Sweden, result in a delay in the acquisition of early writing skills. Delayed development is also noted in the case of children from relatively poor home backgrounds who do not attend preschool prior to entry to school, as in the case of children in a remote rural area of Northern India. However, there are close similarities in development between children of the same age in Canada and in Australia, who are either at the end of their senior kindergarten year or in their first year of school. Using "Who Am I?" as a measure of school readiness, it was found that by age six years virtually all children had reached a level of development where they were able to copy geometrical forms and to write at least some letters or words, indicating that they were ready to benefit from a more structured school 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. One appendix is included: (1) Background and Technical Information on Who Am I? (Contains 2 figures, 14 tables, 10 footnotes, and a bibliography.