An increasing number of preschool children exhibit challenging behavior in the classroom. Children enrolled in Head Start are particularly at risk for emotional and behavioral disorders due to numerous risk factors they face. Unfortunately, some preschool teachers are ill‐equipped to manage the challenging behaviors that preschool children exhibit. The current study investigated the effects of an independent group contingency, the Mystery Student Intervention, on improving preschool children's classroom behaviors. An ABAB withdrawal design was employed to determine the Mystery Student Intervention's effectiveness for decreasing disruptive behaviors and increasing appropriate behaviors in three Head Start classrooms. (author abstract)