This study evaluated the use of the Prevent-Teach-Reinforce for Secondary (PTR-SEC) model as an individualized Tier 3 intervention within the School-Wide Positive Behavioral Interventions and Supports (SW-PBIS) in three high school classrooms. Three teaching staff (two teachers and one instructional aide) and three students with autism spectrum disorders participated in the study. The study examined the degree to which the classroom staff implemented the PTR intervention plan with fidelity and its impact on the students' behaviors, using a multiple baseline across participants design. The results indicated that the teaching staff implemented the PTR intervention plan with high levels of fidelity, and their implementation of the intervention plan led to decreases in problem behavior and increases in replacement behavior across all three participating students with ASD. The PTR-SEC teams found the PTR-SEC intervention to be acceptable and satisfactory; all three staff expressed interest in continuing to implement the PTR intervention plan after completion of the study. [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://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]