Early disruptive behavior, IQ, and later school achievement and delinquent behavior.

A series of structural equation model is developed to examine the relationship between early externalizing behaviors (conduct problems, attention deficit) and IQ measured at age 8 years, academic achievement over the period 10 to 13 years, and delinquent behavior to the age of 15 in a birth cohort of New Zealand children. These models indicated that early externalizing behaviors and IQ were related to later academic achievement and delinquent behavior by two quite distinct but highly correlated developmental sequences. In one sequence early conduct problems were predictive of later delinquency but were not directly related to later academic achievement. In the other sequence, attention deficit and IQ were prognostic of later school achievement but were not directly related to delinquency. Further, the apparent correlations between academic achievement and delinquency were adequately explained by the common and correlated effects of early behavior and IQ on later achievement and delinquency. These conclusions remained unchanged when the sample was stratified by gender, and when further explanatory factors were introduced into the model.