Research consistently shows that among young children, poor social skills and problem behaviors can lead to poor relationships with teachers and peers (Boivin et al., 1995), higher risk of academic failure (Buhs et al., 2006), and higher school dropout (Gilliam, 2005). Moreover, prekindergarten (PreK) and kindergarten (K) teachers report feeling underprepared to address students' social-emotional needs (Alkon et al., 2003), and they often have few resources that have been developed with young children in mind. Consequently, there is an unmet need for supporting PreK and K teachers to implement developmentally appropriate, evidence-based, and effective strategies to support children's social-emotional learning (SEL). The field lacks information on how to scale what we know from smaller studies to district- or state-wide practice while maintaining the quality and impact of SEL initiatives. We present findings from an independent evaluation conducted by SRI examining the implementation and impact of the "Pyramid Model" (PM) in one urban and one rural district in the southeast United States. The PM consists of four components: materials and resources to support SEL in the classroom, training for teachers on high-quality SEL teaching practices, Practice-Based Coaching (PBC) supports for teachers that is ongoing and job-embedded, and additional supports for students in need of more intensive support. The model developers trained district coaches to deliver PBC to support teachers' implementation of the PM strategies. The evaluation team conducted two studies to examine impacts of the PM on teachers and students: a randomized controlled trial (RCT) using school-level assignment of PreK teachers, and an RCT using teacher-level assignment of K teachers. Four cohorts of teachers and students participated between 2018 and 2022. Comparison schools and classrooms continued to implement business-as-usual instructional and SEL supports. Participating schools primarily served ethnically and racially diverse student populations with approximately one fourth of the student populations identified as multilingual learners. Participating PreK teachers were primarily white and female with significant experience teaching young children and certifications/degrees in early childhood. Participating K teachers were similar to PreK teachers but were less likely to have degrees in early childhood. The study sample of students matched the population of students at the schools, with a third identified as Black or African American, a fourth identified as Hispanic or Latinx, and a third identified as white. The project met its primary goals of testing the innovative use of district-hired coaches to support teacher implementation of the PM in the classroom and expanding and testing the PM into K classrooms. The evaluation findings support the use of district-hired coaches to coach teachers to fidelity. The impact studies showed small but nonsignificant effects on teacher-reported math skills (PreK only) and students' social problem-solving skills (K only), suggesting the promise of the PM intervention for improving the social-emotional competence of the youngest learners and supporting academic learning and success. An important contextual factor is that teachers' implementation of the PM and data collection activities were interrupted by the COVID-19 pandemic.