The experiences and learning opportunities children are exposed to in pre-K give them a boost as they enter school. However, the positive effects of pre-K attendance on children's academic and cognitive skills become smaller and sometimes disappear by third grade due to non-attenders "catching-up" to their peers. To make pre-K programs more effective, it may be key to create policies and practices that strengthen instruction to support children's unconstrained skills, such as vocabulary, problem-solving and critical thinking. This brief examines patterns of children's performance on assessments of different types of skills in the fall and spring of kindergarten for children who attended pre-K and their classmates who had no prior pre-K experience. The authors explore factors that may be related to reasons why growth in pre-K attenders' skills slows during the kindergarten year, in turn helping non-attenders quickly "catch up" to their peers. This brief concludes by providing recommendations for policy and practice.