Our study assessed the outcomes of implementing a researcher-developed, teacher-led preventive program in special education preschool classrooms. We evaluated outcomes that were specific to student behaviors, classroom climate, and teacher self-efficacy. As iterative components of the Pyramid Model, an early-childhood-focused iteration of the Positive Behavior Intervention and Supports framework, the intervention focused on teaching, modeling, and reinforcing behavior expectations using research-based strategies deemed effective at supporting the autistic population. Participants in our study included seven special education preschool classrooms, each composed of approximately five students, one teacher, and two teacher assistants. While the student population included those with various disabilities, the majority were diagnosed with or displayed characteristics of autism. Four classrooms implemented the modified program, while three served as controls for comparison. Using a single-case methodology and multiple baseline design, we examined outcomes using visual inspection and nonparametric quantitative analysis (Tau-U). Our preliminary findings indicated improvements in behavioral skill acquisition for students in classrooms where the intervention was implemented. We consider the utility of a tiered-prevention framework with special education populations and its implications on student behavior.