Following the implementation of Tier 1 and Tier 2 Positive Behavior Support (PBS) strategies in six Head Start (HS) classrooms, three children in two classrooms were identified who had significant behavioral challenges and met the criteria for the use of individualized PBS. The purpose of this demonstration was to evaluate whether the effects of individualized PBS intervention implemented by HS classroom staff would have a generalized effect on inappropriate and appropriate behaviors, defined both individually for each child in a support plan and globally across three children. Following intervention with all three target children, both individually and globally defined inappropriate behavior showed decreases over baseline levels, whereas individually and globally defined appropriate behavior showed increases over baseline levels. Overall fidelity was high for implementation of prevention strategies but varied by child and classroom. Social validity ratings indicated that intervention strategies were feasible for use in classrooms and had positive effects on students and staff. (author abstract)