Schools serve a large number of autistic children, yet face two critical gaps that stifle the delivery of evidence-based practices: 1) an intervention gap characterized by limited availability of evidence-based practices educators can use to address externalizing behaviors when they occur in the classroom; and 2) an implementation gap consisting of insufficient evidence-based practice fidelity and sustainment over time. To address these gaps, this project proposes a hybrid type 2 effectiveness-implementation trial that simultaneously tests: 1) the clinical effectiveness of an efficient, educator-delivered clinical intervention to reduce autistic children's externalizing behaviors (Research Units in Behavioral Interventions in Educational Settings; RUBIES), and 2) the implementation effectiveness of an organizational implementation strategy designed specifically to enhance sustainment of evidence-based practices in public schools (Helping Educational Leaders Mobilize evidence; HELM). Consistent with the National Institute of Mental Health (NIMH)'s experimental therapeutics approach, the project also examines the mechanisms through which RUBIES impacts clinical outcomes and through which HELM influences implementation outcomes. The proposed study directly responds to high priority research areas of the US Department of Health and Human Services Interagency Autism Coordinating Committee's Strategic Plan for Autism Research, which calls for expanded research on the translation of proven-efficacious interventions into the community, NIMH Strategic Priority 3.3 to test interventions for effectiveness in community practice settings, and NIMH Strategic Priority 4.2 to expedite adoption, sustained implementation, and continuous improvement of evidence-based mental health services. If successful, this study will have substantial public health impact because it will produce an effective intervention for a prevalent problem among a high impact population in schools across the United States of America and will determine how to sustain this (and other) intervention(s) with high fidelity, to the betterment of health.