For the past dozen years, the federal government has held schools accountable for students' achievement in reading and mathematics. Schools that have not demonstrated improved student scores have faced heavy sanctions, including reconstitution and closure. In response to this high-stakes environment, schools appear to have extended the time students spend in instruction in various ways. In this article, the authors develop a typology of the programs and reforms that extend instruction along three dimensions: time, target, and providers. On the time dimension, extended instruction can occur within a school day or outside of it. Along the target dimension, some types of extended instruction are delivered to all of a school's students while others target particular subpopulations, such as those who have failed to meet certain performance thresholds. Finally, extended instruction may be provided by a school's core instructional staff or by others, including specialized teachers, private providers, and peers. Through the typology, the authors provide a framework for understanding schools' instructional responses to federal accountability requirements and set forth a research agenda that calls attention to unanswered questions about the effectiveness and equity of instructional time interventions.