From the abstract: "As policymakers contemplate expanding preschool opportunities for low-income children, one possibility is to fund 2, rather than 1 year of Head Start for children at ages 3 and 4. Another option is to offer 1 year of Head Start followed by 1 year of pre-K. We ask which of these options is more effective. We use data from the Oklahoma pre-K study to examine these two “pathways” into kindergarten using regression discontinuity to estimate the effects of each age 4 program, and propensity score weighting to address selection. We find that children attending Head Start at age 3 develop stronger prereading skills in a high-quality pre-kindergarten at age 4 compared with attending Head Start at age 4. Pre-K and Head Start were not differentially linked to improvements in children’s prewriting skills or premath skills. This suggests that some impacts of early learning programs may be related to the sequencing of learning experiences to more academic programming..."