The early years from birth to age 8 are a crucial period for children's learning and development. High-quality early childhood education and care (ECEC) and continuity from ECEC into school provide children with a strong foundation for lifelong learning. Understanding how language and cognition skills develop during this period of a child's life can help teachers, educators, leaders and policymakers optimise the support offered to children. This report details findings from the early childhood element of the 2022 Literacy and Numeracy project conducted by the Australian Education Research Organisation (AERO). This element used national linked data from the Australian Early Development Census and National Assessment Program -- Literacy and Numeracy to understand how children's learning and development progresses in the early years of school, including: (1) analysing children's skills on school entry and how they relate to later literacy and numeracy outcomes; and (2) identifying the specific areas of literacy and numeracy where children need the most support. AERO is using the insights from this project to develop practical, evidence-based resources to support and enhance teaching and learning of these skills in schools. [AERO acknowledges that this publication was made possible by the joint funding it receives from Commonwealth, state and territory governments.]