This is the first of two reports that summarize the findings from an impact evaluation of a violence prevention intervention for middle schools. This report discusses findings after 1 year of implementation. A forthcoming report will discuss the findings after 2 years and 3 years of implementation. In 2004, the U.S. Department of Education (ED) contracted with RTI International (RTI) and its subcontractors, Pacific Institute for Research and Evaluation (PIRE) and Tanglewood Research, Inc., to conduct an evaluation of a hybrid intervention model that combines a curriculum-based program, Responding in Peaceful and Positive Ways (RiPP [Meyer and Northup 2002a, 2002b, 2006]), and a whole-school approach, Best Behavior (Sprague and Golly 2005). The combined intervention was administered over the course of 3 successive years. Using a randomized control trial design (with entire schools randomly assigned either to receive the intervention or not), the evaluation assesses the intervention's effects on student violence and victimization and whether these effects vary by levels of student risk. Tanglewood Research, which assisted in the process by which the programs under study were selected, provided implementation oversight along with site-based liaisons and coordinated training and technical assistance for staff in intervention schools. The developers of the two programs that constitute the intervention--Prevention Opportunities and University of Oregon--provided the program materials and conducted staff training. Appendices include: (1) Survey Instruments; (2) Defining the High-Risk Student Subgroup; (3) Construction of Outcome Measures; (4) Statistical Precision; (5) Baseline Measures for Gender Subgroups; and (6) Unadjusted Means and Standard Deviations for Impact Variables. (Contains 53 tables, 4 figures and 17 footnotes.) [This report was prepared for the National Center for Education Evaluation and Regional Assistance, Institute of Education Sciences under contract with RTI International, the Pacific Institute for Research and Evaluation (PIRE), and Tanglewood Research, Inc.]