Many low-performing schools across the nation have increased learning time in response to federal requirements for the School Improvement Grant (SIG) program. The conditions governing federal waivers of the Elementary and Secondary Education Act (ESEA) also require certain schools to redesign the school day, week, or year to include additional time for student learning and teacher collaboration. Furthermore, the waivers allow greater flexibility to redirect certain federal funding streams toward increased learning time. This report by the Center on Education Policy (CEP) at the George Washington University summarizes the findings of a series of case studies of 17 low-performing schools within 11 school districts in four geographically dispersed states--Connecticut, Colorado, Oregon, and Virginia. This research examined state and local efforts to expand learning time through the unique lens of state and local responses to specific federal provisions. In particular, we investigated the strategies being used by the case study sites to meet federal requirements and encouragements for increased or expanded learning time, and the challenges, successes, and impacts associated with this implementation process. All four states in this study have been granted ESEA waivers. Most of the case study schools received SIG funds and/or were identified as "priority" schools under ESEA waivers, meaning that they were among the lowest-performing schools in their state. From October 2013 through March 2014, CEP staff and consultants visited all of the participating districts and the majority of participating schools. We interviewed 49 education leaders, including 13 state education officials, 18 district leaders, and 18 school principals. We also gathered information from state ESEA waiver applications and other relevant state, district, and school policy documents. As explained later in this report, different federal initiatives use different terminology and definitions for provisions that have the common goal of adding time for student learning and for teacher collaboration, professional development, or planning. For simplicity's sake, this report uses the umbrella term of "expanded learning time," or ELT, to describe these various approaches. Throughout this report, the findings are supported by examples from specific districts and schools. Key findings included: (1) Case study schools are meeting the federal requirements to expand learning time, but ELT is costly, and the short-term nature of federal grants is causing difficulties for some schools; (2) Case study districts and schools differ in when and how they expand learning time; (3) State, district, and school leaders participating in these case studies often emphasized that improving the quality of instruction in low-performing schools was just as important as increasing the quantity of instructional time; (4) There was evidence of improved student outcomes in some, but not all, of the case study schools; however, several schools were in the early stages of ELT implementation at the time of the study; (5) Few case study districts and schools were taking advantage of the flexibility afforded by waivers to redirect certain federal funding streams to ELT; (6) States and districts varied in their level of involvement and support for ELT initiatives in schools; (7) Implementing ELT sometimes required negotiations with teachers' unions about such issues as contractual time and compensation; and (8) Teacher and student fatigue from longer school days was cited as a challenge in implementing ELT in all four states studied. More detailed information can be found in the individual reports developed by CEP for each of the four states and 11 districts. These detailed reports, plus three appendices, are available on the CEP website (www.cep-dc.org). [This report was written with the assistance of Nancy Kober.]