This study sets forth the RAND statistical analyses determining both the areas of significant progress in the New American Schools scale-up of implementation of its whole-school reform designs, and various other areas in need of additional attention. New American Schools (NAS) was founded in 1991 as a private, non-profit organization dedicated to whole-school reform. NAS’s mission is to help schools and districts significantly raise the achievement of large numbers of students with whole-school designs and the assistance design teams provide during the implementation process. NAS is currently in the scale-up phase of its effort in which the designs are being widely diffused in partnering jurisdictions across the nation. An earlier report, Implementation and Performance in New American Schools, by Berends, Kirby, et al. (2001) provided an overview of the progress in implementation and performance in a longitudinal sample of schools three years into the scale-up phase. This report provides an update on the progress of implementation a year later. These schools adopted one of seven NAS designs and are located in one of seven jurisdictions that chose to partner with NAS at the beginning of the scale-up phase. The study focused on three research questions: What was the level of implementation in NAS schools four years after scale-up and how has this changed over time? What factors impeded or facilitated the implementation of NAS designs in these schools? Among schools that dropped the NAS designs, what factors contributed to this decision? The report makes clear that several factors need to be aligned for designs to be well-implemented in schools: strong principal leadership, teachers who support the designs and have a strong sense of efficacy, strong district leadership and support, and clear communication and assistance from design teams. Without strong implementation, the promise of these designs to help schools improve is unlikely to be met. These are sobering and important lessons for federal, state, and local efforts aimed at comprehensive school reform. (PA)