This paper uses experimental data from the HSIS to examine the relative impact of Head Start compared to other care arrangements for Head Start-eligible children, including other center-based care, other non-parental care, and parental care. Since the randomization in the HSIS was conducted over the eligibility to enroll in Head Start but not other specific care arrangements, a direct comparison of Head Start to other specific arrangements would be internally invalid. Moreover, children in the HISIS control group chose various care arrangements, and children in the treatment group would have chosen different arrangements if they had been assigned to the control group. Therefore, a direct comparison of children with a specific care arrangement in the control group to all Head Start participants in the treatment group would result in biased impact estimates. To address this issue, this paper uses principal score matching to estimate the probabilities of choosing different care arrangements for children in the control group, and then apply the predicted parameters to the treatment group to estimate the probabilities of having these arrangements for Head Start participants if they had been assigned to the control group. Children with similar principal scores within the treatment and control groups are then matched and their mean outcomes are compared. The findings can provide important information for policymakers to understand whether Head Start works when compared to other specific care arrangements and to help them make decisions on allocating scarce public funds to Head Start and other specific child care programs.