The Growth Model Pilot Project (GMPP) was initiated to allow states to experiment with adjustments to the No Child Left Behind Act (NCLB) status accountability system in order to improve the validity of AYP determinations by giving schools credit for students who are making significant growth. The pilot allowed states, districts, and schools to count students who were on track to being proficient (but not yet there). Under NCLB, such students are not counted as proficient for the purpose of adequate yearly progress (AYP) determinations. The pilot was initiated in November 2005 with the goal of approving up to ten states to incorporate growth models in school AYP determinations under NCLB. No longer a pilot, the project was written into regulation in late 2008; now any state may apply to use a growth model meeting certain core principles. Currently 15 states are implementing growth models under this authority: Alaska, Arizona, Arkansas, Colorado, Delaware, Florida, Iowa, Michigan, Minnesota, Missouri, North Carolina, Ohio, Pennsylvania, Tennessee, and Texas. The purpose of the present study was to determine whether there was any effect, and the kind of effect, of application of the growth models; to provide information about how to strengthen the use of growth under the Elementary and Secondary Education Act (ESEA); and to provide information for states that might consider applying to use a growth model under current regulations. This interim report analyzes the effects of growth models in the first eight states approved under the pilot, for the 2006-07 school year: Alaska, Arizona, Arkansas, Delaware, Florida, Iowa, North Carolina, and Tennessee. Specifically, this study is designed to address three questions: (1) How have states in the pilot implemented growth models? (2) How does each pilot state's growth model affect the number and kinds of schools that make AYP? and (3) What are the implications of the pilot experience for strengthening the use of growth within the context of NCLB? This report divides into four chapters. The introductory chapter considers how the GMPP models compare with status models in approaches to evaluating student achievement. Chapters II and III consider, for each of eight pilot grantee states in the 2006-07 school year, the impact of the state's GMPP model on its AYP determinations. Chapter IV addresses a number of hypothetical questions about how results might change if the data collected as part of the pilot project were used differently. A final project report is planned to address the same research questions with data collected for the 2007-08 school year for all eight states plus Ohio, as well as additional questions about the impact of technical features of the models which are not addressed in the current report. Among the findings were that growth models enabled additional schools to make AYP, but overall percentage increases were not large; the impact of growth models varied widely across states; and most (but not all) schools that made AYP by status would also have made AYP under the growth model alone. The implications for improving use of growth in accountability systems are that states could report both status- and growth-based AYP determinations for all schools in order to give a more complete picture of schools' true performance, including both current performance and whether they are on-track to proficiency in the near future. Appended are: (1) Comparison of GMPP Growth Models with State Accountability Systems; and (2) State GMPP Model Summaries. (Contains 45 exhibits and 27 footnotes.) [This report was prepared for the U.S. Department of Education with the National Opinion Research Center at the University of Chicago.