The ECLS-K is a longitudinal study that followed the same children from kindergarten (5 - 6 years) through the eighth grade (13 - 14 years) in the United States. The children in ECLS-K came from either full-day or part-day kindergarten programs in public or private schools for the academic year of 1998 - 1999. The sample is nationally representative and includes diverse socioeconomic and racial and ethnic backgrounds. Information was collected in the fall and spring of kindergarten (1998-99), the fall and spring of 1st grade (1999-2000), the spring of 3rd grade (2002), the spring of 5th grade (2004), and the spring of 8th grade (2007), and also participating in the study were the children's parents, teachers, and schools.