The National Longitudinal Transition Study (NLTS) 2012 is a national study of nearly 13,000 youth with and without an individualized education program (IEP). These students were chosen to represent all students with and without an IEP in the United States in grades 7 through 12 (or secondary ungraded classes). Among the youth with an IEP are students who represent each of 12 disability categories recognized by the Individuals with Disabilities Education Act (IDEA) 2004. Among the youth without an IEP are students who represent those with no identified disability and those who receive disability accommodations through Section 504 of the Rehabilitation Act (but not IDEA special education services). The study surveyed youth and their parents in 2012 or 2013 when the vast majority (97 percent) of the former were 13 to 21 years old. It spans multiple ages and grades to provide a broad view of students' school experiences at a point in time. This volume focuses on youth with and without an IEP who were enrolled in school in the year they were surveyed. The analysis uses data from 11,853 parent surveys and 10,144 youth surveys, and excludes more than 1,000 youth who were no longer enrolled in school in the year in which they were surveyed. The findings are based on comparisons of averages for all youth with an IEP and three groups of youth without an IEP, namely all youth without an IEP, those with a 504 plan but no IEP, and those with neither a 504 plan nor an IEP. Differences that are statistically significant (not due to chance) and at least 5 percentage points are highlighted to call attention to those that are substantive and policy relevant. The volume addresses the following five research questions: (1) What are the background characteristics of youth and the schools they attend?; (2) What challenges do youth face relating to health, functional abilities, and independence?; (3) How engaged are youth in school and with friends?; (4) What academic supports do youth receive?; and (5) How are youth preparing for life after high school? Appendices include: (1) Technical Notes and Methodology; (2) Detailed Tables for Chapter 2; (3) Detailed Tables for Chapter 3; (4) Detailed Tables for Chapter 4; (5) Detailed Tables for Chapter 5; and (6) Detailed Tables for Chapter 6. [For the Executive Summary, see ED573341.]