At each annual assessment at ages 12–17 mother-reported externalizing behavior was assessed using the Achenbach Child Behavior Checklist (CBCL; Achenbach, 1991c). Mothers were asked whether a series of 33 items on the Externalizing Behavior subscale (e.g., gets in many fights, destroys things belonging to others) described their children in the past six months on a three-point scale anchored 0 (not true) to 2 (very true or often true). At ages 12 and 13, teacher-reported externalizing behavior was assessed using the Achenbach Teacher Report Form (TRF; Achenbach, 1991a). Classroom teachers who knew the target child best were asked how well a series of 34 items on the Externalizing Behavior subscale described target children using the same three-point scale as listed above. The Achenbach manual reports excellent psychometric properties for the CBCL and TRF externalizing scales, including high test-retest reliability, and convergent and divergent validity (Achenbach, 1991a, 1991c). Separate mother and teacher externalizing symptom sum scores for each age were used in longitudinal linear mixed modeling analyses (described below). Alphas across years ranged from .88 to .92 for mother reports and .95
