Challenging behavior in preschool is a serious concern for teachers. In recent years, positive behavior support (PBS) has been shown to be effective in reducing such behaviors. Class-Wide Function-related Intervention Teams (CW-FIT) is a specific program for implementing PBS principles in classroom settings. CW-FIT is a group contingency that utilizes social skills training, teacher praise, and positive reinforcement to improve student behavior. Students are taught specific social skills and then work in teams to earn a group reward based on the use of these skills. CW-FIT has been shown to be effective in elementary classrooms but has not yet been evaluated with other age groups. The present study examined the effects of CW-FIT implementation on teacher praise rates and student engagement in four preschool classrooms with 55 total students. A single-subject, multiple-baseline design with embedded reversals was used to evaluate impact. Results indicate that CW-FIT increased teacher praise rates and student engagement while reducing student disruptive behavior. Both teachers and students found CW-FIT to be socially valid. The present study indicates promising results for the implementation of CW-FIT in a preschool setting. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]