A better understanding of factors influencing who receives disability support services through an Individualized Education Program (IEP) or a Section 504 Accommodation Plan from the Rehabilitation Act of 1973 (504 plan) and when is needed. This study used administrative data from11,405 students enrolled in 121 Baltimore City Schools (51% male; 85% African American; 83% low-income) and longitudinal latent class analysis (LLCA) to identify latent classes of youth receiving disability support services in kindergarten-3rd grade and examine predictors of service receipt. Binary indicators of disability support service receipt were created based on whether the child received services through an IEP or 504 plan in kindergarten-3rd grade. Predictors included sex; race/ethnicity; income level; kindergarten entry age; kindergarten readiness scores in seven domains and whether they were English language learners (ELLs) or participated in public preK. LLCA identified three classes: "always receivers" receiving disability support services every year (9.2%), "late enterers" initiating disability support services in 2nd grade (6.5%), and "never receivers" (84.2%). Classes differed by sex, race/ethnicity, ELL status, preK participation, and 4 of 7 kindergarten readiness domains. Further, males who were not socially behaviorally ready to learn in kindergarten were significantly more likely to be in the "always receiver" and the "late enterer" classes compared to the "never receiver" class. Findings reveal heterogeneity in the timing of receipt of disability support services and demonstrate the potential for preK participation and use of kindergarten readiness assessments to support earlier identification of students needing disability support services.