This report describes and analyzes how eight state education agencies in the Northeast and Islands Region (Connecticut, Maine, Massachusetts, New Hampshire, New York, Puerto Rico, Rhode Island, and Vermont) identify and support low-performing schools and districts under the No Child Left Behind Act of 2001 (NCLB). Data collection for the report began in July 2007 and was completed in April 2008. A research team interviewed senior state education agency officials responsible for state interventions, conducted focus groups with staff and consultants who work directly with schools and districts, and examined materials and documents made public by the state education agencies. Focusing on direct state supports and interventions, the report finds that the eight agencies have created supports and rationales to put federally defined accountability principles into practice in response to their specific contexts, local needs, and capacities. Yet they share common concerns about balancing the tension between state and local decision-making, managing limited financial and human capacity for intervention, and ensuring coherence among various interventions. The state education agency officials' voices and perspectives point to the need for continued learning about building school and district capacity to improve student achievement, and about the role of state education agencies in supporting that goal. Four appendixes are included: (1) Glossary; (2) The No Child Left Behind Act of 2001 and State Accountability Systems; (3) Methods; and (4) Summaries of Interventions and Rationales for each State Education Agency. (Contains 2 notes, 2 boxes, and 16 tables.) [This report was written with Charlotte North. It was prepared for the National Center for Education Evaluation and Regional Assistance, Institute of Education Sciences (IES) by Regional Educational Laboratory Northeast and Islands administered by Education Development Center, Inc. For the report summary, see ED504359.]