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. (author abstract)