The purpose of this study was to examine the effects of Positive Behaviors Support (PBS) plan that was designed after interviews with teachers and Functional Behavioral Assessment (FBA) on the behavior of obeying classroom rules. The study was conducted in a public school with 3rd grade students. There were 34 students in the classroom. PBS was implemented as a whole class but the data were collected from one male and one female student who were identified after FBA and consulting with the teacher. Single subject ABAB design was used to examine the effects of PBS intervention. Experts on the field of special education and the teacher planned the study cooperatively and the teacher implemented the plan in the classroom. The PBS package consisted of prevention strategies, classroom rules, routines and reinforcement. The result showed that PBS package, which was enriched by FBA, was effective on increasing students' behavior of obeying classroom rules. Teacher and family opinions support the findings, too.