This report describes work using nationally representative 2005 data from the School Nutrition Dietary Assessment-III (SNDA-III) study to develop a simulation model to predict the potential implications of changes in policies or practices related to school meals and school food environments. The model focuses on three domains of outcomes: (1) the nutritional quality of reimbursable meals as served to (or selected by) students in the NSLP (National School Lunch Program) and SBP (School Breakfast Program), (2) the nutritional quality of the breakfasts and lunches consumed by children who participate in these programs, and (3) student participation rates. The model was intended to assist FNS (Food and Nutrition Service) in assessing the effects of the IOM (Institute of Medicine) panel's recommendations and other possible changes in school meals and the school food environment. The report is organized as follows: Chapter I presents the introduction and the conceptual framework for the study; Chapter II briefly describes the SNDA-III data and discusses the issue of linking SNDA-III data to cost data; Chapters III and IV describe the development of policy/practice indicators that were used to simulate changes targeted at specific food and nutrient outcomes; Chapter V describes the development and estimation of predictive models for each of the three outcome domains; Chapter VI describes how the results of these predictive models were combined into a single simulation model that enables users to examine the consequences of alternative program policies or practices for the characteristics of meals served and consumed, and program participation; Chapter VII discusses the specification and simulation of three specific policy reforms and presents the simulation results; Chapter VIII describes a number of sensitivity analyses designed to test the robustness of the overall models and simulation results, and presents results from these analyses; and Chapter IX summarizes the report and discusses avenues for future research. Appendices include: (1) Details and Results of Exploratory Analyses to Select Policy and Practice Variables; (2) Regression Results for Baseline Models and Sensitivity Analyses; (3) Simulation Results; and (4) Sensitivity Analyses: Simulation Results. A glossary is included. Individual chapters contain footnotes. (Contains 70 tables and 1 figure.) [This report was submitted to the USDA, Food and Nutrition Service, Office of Research and Analysis.]