Participants in the CDP were originally recruited from 3 cities (Nashville and Knoxville, Tennessee, and Bloomington, Indiana) during kindergarten preregistration in 1987 and 1988. Within each site, about 6 schools that served families from a range of socioeconomic status groups were selected to participate, explicitly including schools in economically at-risk neighborhoods. Most of the sample was enrolled by randomly approaching parents at preregistration and inviting them to participate in a longitudinal study of child development, with-approximately 75% agreement. Because a small percentage of children in the targeted schools do not preregister (15%), a similar proportion of the CDP sample was recruited on the first day of school or through a letter or telephone call to maintain representativeness of the school population. This procedure produced a participant sample that validly represented the broader population demographically and behaviorally, as determined by teacher and sociometric ratings of the entire population at those sites. The original CDP sample consisted of 585 children (52% male; 81% European American, 17% African American, and 2% belonging to other ethnic groups). More than 20% of participants were born
