To develop and support teachers' skills in classroom management, resource-efficient teacher training approaches are needed. This study evaluated the effects of an online tiered training intervention on teachers' use of class-wide positive behavior supports, either behavior-specific praise (BSP) or opportunities to respond (OTRs), using a randomized controlled trial conducted in an online graduate course in classroom management. Fifty-nine participants (52 teachers, 6 paraprofessionals, and 1 after-school instructor) completed the study. We randomly assigned 29 teachers to receive tiered training for BSP and 30 teachers to receive tiered training for OTRs. We found tiered training increased participants' use of the target practice, BSP or OTR, with medium to large effect sizes, and most teachers required support beyond universal training. Teachers rated the training they received as highly acceptable, feasible, and useful.