The major issues involved in the design and implementation of effective school screening programs are addressed, using data from a longitudinal study following over 500 children from preschool through third grade. The article identifies early characteristics of children that are related to later behavioral and emotional problems, assesses the accuracy of a comprehensive screening procedure for identifying such problems, and compares two models using preschool and kindergarten data. Characteristics of children missed by the models are presented, and labeling issues are addressed. Implications for future screening efforts, policy, and research are discussed.