The major aims of this project were to: 1) Adapt for middle schools and assess the feasibility and acceptability of the Maryland Safe and Supportive Schools (MDS3) Model; 2) Test the efficacy of MDS3 for improving school safety and climate, problem behaviors, engagement, and achievement using a group of randomized controlled trial design in 20 middle schools; and 3) Measure the programmatic costs and benefits associated with implementation of the MDS3 model. Toward that end, during Spring 2015, the study team adapted and finalized the middle school version of Maryland Safe and Supportive Schools (MDS3) model, ensuring that it was feasible and acceptable to implement in middle schools, thereby addressing aim 1. The study team then began a randomized controlled trial in Summer 2015, whereby they recruited, enrolled, and randomized 40 middle schools to intervention and control conditions. The study team then collected baseline (Spring 2015- Fall 2015) and annual follow-up data in the Spring of the 2015-2016, 2016-2017, and 2017-2018 school years. These data included: student, staff, and parent indicators via the online MDS3 School Climate Survey; implementation of positive behavior supports and multi-tiered interventions; classroom and environment observations using two measures: Assessing School Settings: Interactions of Students and Teachers (ASSIST; Rusby et al., 2001) and School Assessment for Environmental Typology (SAfETy; Bradshaw, Milam, Furr-Holden, and Lindstrom Johnson, 2015); and cost data assessing the cost of program delivery in all 40 schools. Additionally, the team collected implementation data from coaches in the 20 intervention schools, which included information on coaching fidelity and ratings of the school engagement.