Development of the TAGG began in 2007 with creation of the basic idea, collection of initial research studies, and social validation studies of the basic concept. A grant award from the National Institute of Education Science’s National Center for Special Education Research provided the funding to bring together an involved group of assessment experts and transition professionals to create the TAGG. The following chapters of the TAGG Technical Manual describe the iterative development process that produced the TAGG assessment and results of various validity studies. We developed the TAGG following the steps detailed in the Standards for Educational and Psychological Testing (1999) by the American Educational Research Association, American Psychological Association, and the National Council on Measurement in Education. The Technical Manual Chapters will be updated as additional validity evidence becomes available.