The application of Response to Intervention (RtI) to early childhood settings presents many opportunities and challenges; however, it remains unclear how best to implement this framework in settings in which children at risk of academic difficulty are overrepresented, like Head Start. One of the first steps in implementing any RtI process is the effective and efficient identification of children who are in need of additional instructional support (e.g., Tier 2 or Tier 3). This process is critical as it directly affects the amount of resources needed to support children appropriately--a factor that is particularly concerning for programs that primarily serve children who are at risk of social, emotional, or academic failure difficulties. The purpose of this study was to investigate the proportion of at-risk children who may be in need of additional instructional support when screening and norm-referenced measures are administered at the beginning of the year. In addition, the proportion of at-risk children who continued to need additional support after receiving approximately 6 months of Tier 1 instruction was examined. (author abstract)