Early in 2003, the National Assessment Governing Board established the National Commission on the National Assessment of Educational Progress (NAEP) 12th Grade Assessment and Reporting, following the recommendation of retiring Governing Board Executive Director Roy Truby. The Governing Board's charge to the Commission was "To review the current purpose, strengths, and weaknesses of 12th grade assessment and reporting by the NAEP and set forth recommendations for improvement to the National Assessment Governing Board." The Commission was instructed to focus on improvements needed for 12th grade NAEP and not on the status of high schools generally or the quality and rigor of the high school curriculum. The Commission has attempted to heed this guidance scrupulously. The Commission has met and deliberated five times since March 2003. It focused on answering the following questions: What do we know about 12th grade achievement, what do we need to know, and what can NAEP provide? The Commission received expert testimony from twenty-four witnesses, commissioned and reviewed six white papers and two research studies, conducted a focus group with the Council of Chief State School Officers, and received comments on preliminary Commission recommendations from the National Association of State Boards of Education and Tennessee state education leaders. This report presents the reasons for the Commission's conclusion that 12th grade NAEP should be redesigned and makes recommendations towards the creation of a systematic strategy to increase school and student participation in grade 12 NAEP. The report observes that NAEP's leaders must focus seriously on increasing participation or face the prospect that the quality and credibility of the 12th grade NAEP achievement results will be compromised. (Contains 1 table.)