Teachers from fourteen classrooms were randomly assigned to an adaptation of Incredible Years (IY) teacher training or to teacher training-as-usual. Observations were made of the behavior of 136 target preschool boys and girls nominated by teachers as having many or few conduct problems. Peer and teacher behavior were observed at baseline and post training. IY training resulted in increases in teachers' positive and reductions in teachers' negative behavior relative to training as usual, in decreased peer negative behavior toward target children, and in decreased negative behavior of target children high on conduct problems. The impact of IY training on the behavior of target children was mediated by changes in peers' behavior with no direct effects of teacher behavior and differential effects for high and low conduct problem children. Teacher training focused on altering the whole classroom environment may be an effective strategy, even for children with significant conduct problems.

The prospective relationships of conduct problems and peer coercion and deviancy training during kindergarten (mean age = 5.3 years) to overt and covert conduct problems in third-fourth grade were examined in a sample of 267 boys and girls. Coercion and deviancy training were distinct peer processes. Both were associated with earlier child conduct problems but were differentially associated with child impulsivity, verbal ability, anxiety, peer rejection, and deviant peer affiliation. Coercion by peers predicted overt conduct problems and peer deviancy training and the interaction of deviancy training and coercion predicted covert conduct problems in third-fourth grade. Peer deviancy training occurs in early childhood and may serve as an independent risk mechanism in addition to peer coercion for early-onset, persisting conduct problems.