Using two paired datasets from the Head Start Program Information Report and Migrant and Seasonal Head Start (MSHS) Study, this study explored disparities in program rates of screening, referral, and identification for early intervention between MSHS and Head Start programs, as well as associations between MSHS teacher ratings of children's communicative risk, latent and manifest dimensions of disability coordination, and children's language and literacy outcomes. Results from program-level analyses of MSHS and HS disparities showed that MSHS programs screened more, but referred and identified fewer children. Disparities in identification persisted even in the presence of demographic controls. Post-hoc sensitivity analyses showed MSHS identification rates were negatively moderated by rurality. Additionally, multilevel analyses of MSHS study data revealed that MSHS teacher ratings of children's communicative risk were positively associated with their language and literacy skills. Confirmatory factor analysis and subsequent structural equation modeling of disability-related survey items revealed parent engagement was modestly related to preschoolers' English-language literacy skills and that teacher professional development for assessment was modestly related to all children's oral language skills. A final set of multilevel analyses incorporating PIR data showed low program-level screening rates were negatively associated with parent-rated expressive language outcomes for infants and young toddlers only. Implications to inform policymaking related to early intervention and preschool for children with or at risk for disabilities and dual language learners are discussed. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]