Background & Context: Developmental theorists and researchers have long argued that children's early skill development is critical to subsequent positive developmental outcomes (Bailey & Jones, 2019; Masten et al., 2006; Cichetti & Rogosh, 2002) and is shaped by ecological contexts (Bronfenbrenner & Morris, 1998). Yet, there is little longitudinal research examining how specific developmental patterns within the social and emotional domains are associated with features of children's home and early education and care (EEC) settings. Increasingly, researchers are using person-centered analytic approaches to examine latent patterns of growth and change in social and emotional skills, as these methods reject the notion that populations are homogenous, and go beyond documenting average trends to illuminate unique and unobserved profiles of developmental trajectories over time (Collie et al., 2019; Huang & Siraj, 2023; McCoy et al., 2018; Weiss et al., 2022). Such approaches can be used to inform equitable early intervention efforts by illuminating children's developmental patterns and providing insight into how children's individual development is influenced by context. This study contributes to and extends these ongoing methodological efforts by investigating how unobserved social and emotional developmental trajectories in early childhood are related to specific observed features of children's early environments that are thought to promote and sustain social and emotional development. Research Questions: The aims of this exploratory study are to contribute to the burgeoning knowledge base on the kinds of contextual features that support the development of social and emotional skills in early childhood. Specifically, our primary research aim is to document the nature and developmental course of social and emotional skill trajectories through early childhood in a statewide sample. Building on this, our secondary aim is to examine longitudinal associations between features of children's early ecological contexts and profiles of social and emotional trajectories. Setting & Participants: Data for this study were collected during the 2017-18, 2018-19, and 2019-20 academic years as a subset of a longitudinal, population study of children's EEC experiences in Massachusetts (Jones et al., 2020). The sample for this study includes 1,511 children who were aged 3 or 4 in 2017-18 and were assessed on at least one of the child skill measures at all three timepoints (see Table 1 for sample characteristics). Children were recruited to the wider study through multiple strategic approaches to ensure sociodemographic and geographic diversity across the state. Data Collection and Analysis: Child data were collected during the first three years of the longitudinal study using a variety of assessment modalities. Children's executive functioning was assessed via direct assessments conducted by trained raters each year. During each wave of data collection, parents also completed surveys that included questions on children's self-regulation and executive functioning, as well as on internalizing, externalizing, and adaptive behaviors. Regarding the contextual features, parents also reported on their relationship with their child, the level of household chaos, and socio-demographic information. Finally, trained observers conducted in-person observations of children's early childhood settings during the first year of the study. Observers used two standardized tools to capture a variety of dimensions of classroom interactional quality; in this study, we include items/subscales pertaining to the emotional supportiveness of the classroom (see Table 2 for information on the measures used in this study). To address Aim 1, we used growth mixture modeling, which allowed us to examine heterogenous growth patterns in social and emotional skills over the three timepoints. This approach assumes that not all people are influenced by variables in the same way and allows for the examination of smaller groups of individuals sharing similar social and emotional trajectories, rather than examining averages across the entire population (Laursen & Hoff, 2006). To address the second research aim, we plan to investigate whether differential social and emotional developmental trajectories are associated with particular contextual features of children's early environments. Specifically, we focus on parent-child relationships, the emotional environment at home, and emotional climate in preschool as predictors of social and emotional trajectory profiles. By examining features in both home and ECE settings, we explore a more holistic understanding of the environments that support and enhance child development. Results: Our initial results indicate that across an array of social and emotional skills, different developmental profiles characterize growth over time. Across the five social and emotional skills, a majority of children in the sample clustered in profiles indicating average and mostly stable levels of development over time, though there were some differential patterns across the different skills in both negative and positive growth directions (see Figures 15 for our preliminary unconditional models illustrating developmental patterns across skills). Currently, we are conducting logistic regression analyses to investigate whether these different trajectory profiles are associated with specific features of home and EEC settings. The final presentation will include results from these analyses to provide insight into the influence of children's early learning ecologies on their development of social and emotional skills. Conclusions: Findings from this study have implications for the field of social and emotional learning (SEL). Since there is little research on trajectories of social and emotional development throughout early childhood, this person-centered, longitudinal study fills a critical gap in knowledge as to how the skills supported by SEL programming and practices emerge across time and importantly, how specific features of children's early learning ecologies contribute to their social and emotional development throughout early childhood. Taken together, the findings from our study suggest there is merit to using person-centered methods to better understand the developmental trajectories of social and emotional skills in early childhood and value in understanding the relationships between children's trajectory profiles and observed features of the home and EEC setting. We hope to expand the discourse on how best to support the development of social and emotional skills by producing rigorous information gleaned from children's lived experience in both home and EEC contexts to inform practitioners, SEL program developers, and policymakers as they consider which contextual features of a child's ecological environment might be most fruitful as targets for equitable early intervention.