Background: A large evidence base suggests that without effective early intervention, young children who exhibit persistent challenging behavior often face a host of long-term social and academic challenges (Bulotsky-Shearer & Fantuzzo, 2011; Hauser-Cram & Woodman, 2016; Kazdin, 1995; Lane et al., 2008; Miller et al., 2017). Challenging behavior is characterized as "any repeated pattern of behavior... interfering with the child's optimal learning or engagement in prosocial interactions with peers and adults" (Smith & Fox, 2003). Some preschool and kindergarten teachers resort to suspending or expelling children (Brock & Beaman-Diglia, 2018); these practices deprive children of learning experiences and may have negative long-term effects, such as disengagement from school, diminished educational opportunities (Adamu & Hogan, 2015; Lochner & Moretti, 2004), and expulsion and suspension in later school grades (Raffaele Mendez, 2003). These interventions come at a critical time to support children's social-emotional development, which has been significantly disrupted by the COVID-19 pandemic. Moreover, early childhood teachers report feeling underprepared to address social emotional needs, while acknowledging that these issues are of utmost concern (Alkon et al., 2003; Benedict et al., 2007; Joseph & Strain, 2003). Consequently, there is an unmet need for ensuring that teachers are equipped to help young children develop necessary social-emotional skills. The Pyramid Model (PM) trains and coaches teachers in evidence-based practices that have demonstrated effectiveness in promoting the social-emotional and behavioral skills of preschool children. However, prior studies have not examined the effects of the PM among kindergarten children. Professional development (PD) emphasizing a strength-based approach to support children's social development may help kindergarten teachers address problem behaviors without using exclusionary discipline and employ more developmentally appropriate supports for building social-emotional competence in their young students. Objective: There is existing evidence of the effectiveness of the Pyramid Model in supporting teachers of preschool children and promoting children's social-emotional and behavioral skills (Hemmeter, et al., 2016; 2021). In this study, we will present findings and discuss implications for extending PM training and Practice-Based Coaching supports to kindergarten teachers. Setting: This study occurred in one mid-sized urban district and one rural district in the southern United States. Participants: The study included 60 teachers in 25 schools and 409 kindergarten children enrolled in their classrooms and whose parents consented for their participation. The Pyramid Model (PM) Intervention: The PM provides early educators with a three-tiered model of classroom strategies that promote social-emotional competence and address challenging behavior of children with and without disabilities in preschool classrooms. The PM includes four components and is based upon research on effective instruction for young children (National Research Council, 2001), the promotion of children's social competence (Guralnick & Neville, 1997; Webster-Stratton, 1999; Hyson, 2004), and the implementation of individual positive behavior support for children with the most severe behavior challenges (Fox et al., 2002). The first two PM components -- responsive interactions and classroom preventive practices -- are universal approaches that are delivered to all children in a classroom. The third component -- social emotional teaching strategies -- offers secondary interventions designed to address the needs of children at risk for problem behavior. The fourth component provides an individualized intervention approach for children with the most severe and persistent challenging behavior. When teachers implement the universal and secondary strategies of the PM, only a small percentage of children are likely to need more intensive supports (Sugai et al., 2000). Research Design: To examine the effects of PM on teachers' practices and children's social competence, we conducted a teacher-level, cluster randomized controlled trial (RCT) with teachers randomized to either the PM (treatment) or to "business as usual" (BAU; control) conditions. In this study, kindergarten teachers in the treatment condition participated in a two-day training and received ongoing biweekly coaching from trained PM coaches and staff for a full school year. Teachers assigned to the control condition were asked to implement their BAU curriculum and activities. Data Collection and Analysis: We collected direct assessments and teacher ratings of children's social-emotional competence, executive functions, problem-solving skills, and academic competence in the fall of the kindergarten year, prior to randomization and teacher training. Direct assessments include Peg Tapping (Diamond & Taylor, 1996; executive functioning), Head Toes Knees Shoulders (Ponitz, et al., 2008) and the Challenging Situations Task (Denham et al., 1994). Teachers provided information about their students' social and academic skills using the Social Skills Improvement System (Gresham & Elliott, 2008) and Academic Rating Scale (Rock & Pollack, 2002), respectively. We will collect all direct assessments and teacher reports again in the spring, after kindergarten teachers in the PM condition have received training and ongoing coaching supports. In addition, the research team completed classroom observations to monitor fidelity of implementation to the PM. Once spring outcome data are collected, we will perform intent-to-treat and treatment-on-the-treated analyses. We will analyze data using two-level HLM models, as students are nested in teachers and teachers are the unit of random assignment. Results & Discussion: In this presentation, we will present findings from our analyses of the impact of the PM on kindergarten child outcomes (to be conducted in summer 2022, after data collection concludes in spring 2022). We will also discuss lessons learned about how to scale up an evidence-based model across a district with district staff, extending that model to kindergarten, and challenges in designing and conducting a rigorous RCT in the context of the COVID-19 pandemic. Results will build on what is known about the effects of the PM by extending evidence to kindergarten classrooms in the context of a sustainability model relying on district-hired coaching staff to train and support teachers.