Little is known about how the expansion of state pre-kindergarten (pre-k) programs affects low-income children with disabilities in Head Start. Using almost 30 years of administrative data of all Head Start programs and a differences-in-differences design, this study tests the possibility that, as state pre-k differentially draws relatively more advantaged children from the pool of eligible 4-year-olds, Head Start taps into their relative programmatic strengths and serves more children with disabilities. (author abstract)