Few mental health initiatives for young children have used classroom programs. Preschool-based efforts targeting externalizing behavior could help prevent conduct disorders. Additional benefits may include improved academic achievement and reduced risk for other mental health difficulties. Pro-grams that target multiple developmental domains are most likely to succeed. However, more research is needed to guide such initiatives, and practical challenges must be addressed. This paper describes an effort to implement and test preschool classroom-based programs aimed at externalizing and academic problems.