Most approaches aiming to reduce behavior problems among youth with Autism Spectrum Disorder (ASD) focus on individual students; however, school personnel also need professional development to better support students. This study targeted teachers' skill development to promote positive outcomes for students with ASD. The sample included 19 teachers in two non-public special education settings serving students with moderate to severe ASD. Participating teachers received professional development and coaching in classroom management, with guided practice in a mixed-reality simulator. Repeated-measures ANOVAs examining externally-conducted classroom observations revealed statistically significant improvements in teacher management and student behavior over time. Findings suggest that coaching and guided practice in a mixed-reality simulator is perceived as acceptable and may reduce behavior problems among students with ASD.