California requires each school district to belong to a Special Education Local Plan Area (SELPA) for special education planning and governance. The California Department of Education (CDE) and the State Board of Education (SBE) are interested in the impact on the surrounding small and midsized districts when large districts become single-district SELPAs. Given one of the original motivations of SELPAs was economies of scale, the state wanted to examine the association between different SELPA types and district configurations and outcomes, including SELPA funding patterns, inclusion rates of students receiving special education services in the general education environment, and academic outcomes for students receiving special education services. This study examined those differences using publicly available data. The findings provide mixed evidence for the possible implications of large districts leaving multidistrict SELPAs to form single-district SELPAs. The study found no meaningful association between different SELPA and district configurations and academic outcomes for students with disabilities--including graduation and dropout rates--and proficiency rates in math and English language arts and on the alternative assessment. Several meaningful differences with regard to funding and inclusion were found. For example, when comparing multidistrict SELPAs with and multidistrict SELPAs without a large district, multidistrict SELPAs without a large district received larger per pupil apportionments and had higher inclusion rates. Also, when comparing small districts in multidistrict SELPAs with and multidistrict SELPAs without a large district, inclusion rates were higher for preK students and lower for K-12 students in SELPAs without a large district. The larger amount of per pupil special education funding in multidistrict SELPAs without a large district may help to alleviate some concern about the impact of large districts separating from surrounding small and midsized districts to become their own SELPAs. The CDE and the SBE may want to further examine which regionalized programs are implemented by SELPAs of different compositions and how they benefit small districts. Further research could consider more complex analyses to better understand the outcomes that may be due specifically to membership in a single-district versus a multidistrict SELPA.