The original vision of Head Start called for a program that would "get kids ready so they would have a chance in school...a chance in life" (Sargent Shriver; quoted in Zigler and Valentine, 1997, p. 59). President George W. Bush's recent emphasis on literacy and school achievement in Head Start highlights the academic aspect of the Head Start mission but threatens to further lower the priority of another aspect of the mission, mental health, which research has shown to be a critical element for academic success and quality of life. Head Start Program Performance Standards have consistently recognized the inter-relationship between mental health and the ability to learn in young children; mental health goals and performance standards were part of the original vision and were reaffirmed most recently in 1998. Mental health performance standards have not been met, and must be if we do not want to compromise the learning and development of a substantial percentage of children. In this paper, we briefly review the history of mental health in Head Start, discuss the relationship between mental health and learning, and describe why, to date, the program has largely failed to address mental health. Model programs, such as the Enhanced Mental Health Program in Ventura County (California) Head Start, demonstrate that it is possible to make the goal of incorporating mental health in Head Start a reality. Further, results suggest that following through on the program's commitment to mental health could be one of the most effective ways to improve academic achievement in Head Start. Children who are anxious, oppositional, traumatized, hyperactive, or depressed are not likely to be able to achieve critical educational standards if their mental health needs are not recognized and treated. Mental health can and should play a major role in Head Start if we are to leave no child behind.