The development of social-emotional competencies in early childhood is essential for long-term health and wellbeing, and these skills are particularly critical for children from disadvantaged backgrounds to set the foundation for success in school and in life. The present study examined the effects of an intervention to support prekindergarten (pre-k) teachers' ability to address the specific social-emotional needs of their students. Teachers in a publicly funded pre-k program completed the Devereux Early Childhood Assessment (DECA; LeBuffe & Naglieri, 1999; LeBuffe & Shapiro, 2004) to measure social-emotional functioning. "Intervention" teachers received summaries of their students' social-emotional strengths and needs based on the DECA and packets providing teaching strategies they could use to target the social-emotional domains assessed by the DECA. Teachers were encouraged to work with their coaches to interpret their classroom summaries and implement strategies to address their students' needs. Multilevel modeling revealed that students whose teachers received social-emotional feedback (classroom summaries and strategy packets) showed significantly greater social-emotional gains (across multiple domains) over the school year compared to students whose teachers did not receive feedback. Our findings suggest that having teachers complete social-emotional assessments of their students at the beginning of the school year and providing teachers with data-based feedback may build teachers' capacity to promote social-emotional development for children from disadvantaged backgrounds. We discuss the potential to build on this data-guided approach to better prepare children to succeed in elementary school and beyond. (PsycInfo Database Record (c) 2021 APA, all rights reserved).