Background/Context: Racially integrated environments are important for young children, because the typical age of a preschool child coincides with the period of development during which a child's basis for racial schemas and their understanding of racial stereotypes form (Piazza & Frankenberg, 2019). However, rates of racial segregation in preschool education are higher than in any other level of education in the K-16 system in the United States (Monarrez & Washington, 2020). This study is designed to shed light on one possible integration strategy that has been largely neglected in scholarly literature and policy discussions--the placement of public early childhood programs. We use the unique opportunity of California's current transitional kindergarten (TK) expansion to examine how the implementation of different TK program structures and attendance boundaries can influence the racial makeup of both TK programs and the elementary schools in which they are located. For school districts given the task of implementing TK programs, decisions about where to locate these classrooms--in centralized hubs or in all schools--may play out differently in different district contexts. For some districts, a hub model with strategically placed TK programs can pull students from neighborhoods with different demographics, creating more diverse TK classrooms. Other districts prioritizing wide access might opt to offer TK in every elementary school. Additionally, bringing high-quality early education to public schools can attract and retain families of all racial backgrounds, and reestablish positive relationships between school districts and parents who may have left the district for private schools. Evidence of this was reported in Washington, D.C., after the district's high-quality universal preK program for 3- and 4-year-olds brought more families back into the public schools (Fiscal Year 2018 PreK Report, 2018); and those students were also more likely to continue to enroll in the public school system for kindergarten (Monarrez et al., 2020). Purpose/Objective/Research Question: In this mixed methods study, we first explored district leader's perspectives on TK expansion and racial segregation through interviews. The key research questions are: (1) How do district leaders make decisions about TK placement policies and structures? (2) What strategies appear to have potential for reducing racial segregation in TK programs? Through a quantitative analysis, we then explore the following research questions: (3) How does the racial makeup of TK programs vary across California? (4) Are certain TK placement policies and structures associated with changes in racial segregation in TK between 2021 and the current year? (5) How could racial segregation change if different TK placement policies or structures were used? Setting: This research takes place in elementary and unified school districts across California. Population/Participants/Subjects: Seven district leaders from districts in diverse parts of California and with different TK contexts participated in the initial exploratory interviews. For the survey, we included all districts (n= 376) in California with at least 4 elementary schools, TK enrollment of at least 20 students, and with no racial/ethnic group representing more than 90% of their TK and elementary school enrollment combined. Intervention/Program/Practice: We explored three TK placement policies and their relationship with levels of segregation. First, we examine the use of hub models to provide TK. Hubs are schools within a district that offer TK programs centrally that serve young students from across the district, or from multiple schools' attendance areas. Students typically attend TK in the hub school and then transition to kindergarten in their home school. Second, we investigate strategies districts may use to recruit more families to the district to take advantage of TK, particularly if there are specific groups who are participating in lower numbers or who have left the district in large numbers. Finally, we investigate whether districts have redrawn school attendance boundaries in the midst of TK expansion. Research Design: The project address the research questions through the following activities--(1) exploratory district interviews; (2) survey of districts statewide to gather information on attendance structures and other TK policies; and (3) a set of quantitative analyses made up of descriptive statistical portraits, simulation models, and econometric analyses to examine the relationships between attendance policies and structures and school (and TK-specific) racial segregation. Bias was reduced in the qualitative work through using a systematic coding review process. Each interview was independently coded by two members of the qualitative analysis team. We also met weekly during data collection to discuss the interview process and whether any questions needed to be adjusted to ensure we are collecting comprehensive data and not leading respondents. For the survey analysis, we analyzed the response status to our survey to identify potential sources of nonresponse bias and adjusted statistical estimates in accordance with recommendations established by survey research. Data Collection and Analysis: We conducted seven 60-minute interviews and one focus group with early education district leaders across the state of California. The interviews were coded using deductive thematic coding methods with a team of four qualitative analysts. All interviews were double-coded. Themes were discussed as an analytic team and consensus was reached on major themes from the codes through weekly meetings. To gather information about themes raised during interviews systematically statewide, we then conducted a survey of Elementary and Unified school districts to gather data on TK placement policies and procedures. Questions asked where TK classrooms were placed and why, how students are assigned to TK schools, whether the district offers programs that intentionally group students with similar backgrounds in one school or program (such as dual language support programs), and whether attendance boundaries were adjusted as a result of TK expansion. We also obtained data from the California Department of Education's (CDE) UPK Planning & Implementation district survey and publicly available TK and Elementary school enrollment data also from the CDE. We examined differences in segregation levels and the racial composition of TK and elementary school enrollment by structure and other policies of interest. We calculated multi-group segregation in terms of evenness using Theil's entropy index H and two-group segregation (Black-White, Hispanic-White and Asian-White) using the Isolation index and describe how these indices vary across the state. We then explored segregation dynamics between TK hub and all-school models through a set of counterfactual exercises. First, we examined how much racial segregation would change if hub districts instead placed a TK program in every school. Second, for districts that place TK programs in all schools, we examined how much racial segregation changes if they instead used a hub model that selects hub and feeder combinations that minimize TK racial segregation. The final component of our analysis examined the impact of TK placement type on public school enrollment and racial segregation using difference-indifferences (DD) regression modelling. The independent variable is TK placement type, and the main outcome variable is Thiel's H measured for TK enrollment. Given that TK expansion has been implemented recently in California, and to understand potential consequences for post-TK continued public school enrollment, we modelled changes in K-2 enrollment patterns as well. Findings/Results: Regarding RQ1, we found the majority of district leaders interviewed did not consider school diversity as they planned for TK expansion. Their concerns around expansion were mostly focused on logistical challenges such as space in current elementary schools and locating age-appropriate facilities for four-year-old students. Regarding RQ2 examining the strategies districts are using to reduce racial segregation in their TK programs, we found that staff professional development opportunities to foster a welcoming environment for all families was the most common strategy. Other strategies mentioned by districts included targeted outreach to recruit and provide program information to specific communities, and using cross-district enrollment programs such as dual-language immersion or hub-based TK sites as strategies to reduce racial segregation. Results from the quantitative analysis will be available late in the summer of 2025 and ready to present by October in time for this conference. Conclusions Conclusions for this work are on-going as the survey will be administered in May 2025. Conclusions and implications for the field will be ready to present for the conference.