Understanding the rapid and episodic learning and development of young children is a complex undertaking. In the early years, each child experiences the most dramatic developmental and learning period in his or her lifetime. In addition, there is marked variability among children in the rate and pattern of typical development. Motor, social-emotional, and cognitive development can follow different trajectories among young children. Meaningful understanding of young children's learning requires setting the best early learning standards possible, asking the right questions about children's growth and development, deciding which assessment strategies will best answer those questions, and using the results in ways that promote effective teaching and improved learning. Yet none of this can be developed and sustained without strong leadership that sets the goals, provides the resources to meet the goals, and promotes and fosters assessment literacy to ensure that teachers and administrators understand the assessment process and know how to use it thoughtfully so that, ultimately, all children experience success in school and throughout their lives.