The present study is a large-scale randomized trial testing the effects of a family-school partnership model (i.e., Conjoint Behavioral Consultation, CBC) for promoting behavioral competence and decreasing problem behaviors of children identified by their teachers as disruptive. CBC is a structured approach to problem solving that involves consultants, parents, and teachers. The effects of CBC on family variables that are commonly associated with important outcomes among school-aged children (i.e., family involvement and parent competence in problem solving), as well as child outcomes at home, were evaluated. Participants were 207 children with disruptive behaviors from 91 classrooms in 21 schools in kindergarten through grade 3 and their parents and teachers. Results indicated that there were significantly different increases in home-school communication and parent competence in problem solving for participants in the CBC relative to control group. Likewise, compared to children in the control group, children in the CBC group showed significantly greater decreases in arguing, defiance, noncompliance, and tantrums. The degree of family risk moderated parents' competence in problem solving and children's total problem behaviors, teasing, and tantrums.