Well over three million children, K-12, are estimated to have lost instructional "seat time" in 2009-2010 because they were suspended from school, often with no guarantee of adult supervision outside the school. That's about the number of children it would take to fill every seat in every major league baseball park and every NFL stadium in America, "combined". Besides the obvious loss of time in the classroom, suspensions matter because they are among the leading indicators of whether a child will drop out of school, and because out-of-school suspension increases a child's risk for future incarceration. Given these increased risks, what we don't know about the use of suspensions may be putting our children's futures (and our economy) in jeopardy. This national report, based on suspensions of students in K-12 in 2009-2010, represents the first major effort to fill the knowledge gap around school discipline as it stands in thousands of districts in nearly every state. Based on data released in March 2012 by the U.S. Department of Education, the authors analyze the risk of out-of-school suspension for every racial/ethnic group, as well as for students with and without disabilities. The report begins by providing national- and state-level estimates, but perhaps the most valuable information presented is the detailed analysis of nearly 7,000 school districts from every state in the nation. In this national database, using the companion spreadsheets, readers will easily locate the highest suspending school districts for each racial group, and for students with and without disabilities. This report demonstrates that, in most districts, the highest risk for suspension is revealed when the data are disaggregated by race and combined with gender and/or disability status. Appended are: (1) Data Omissions; and (2) Methods and Treatment of Errors. (Contains 11 tables, 10 figures and 32 footnotes.) [For "Opportunities Suspended: The Disparate Impact of Disciplinary Exclusion from School. Executive Summary," see ED534184.]