A systemic analysis of early childhood development factors explains the variance in school readiness among representative U.S. 5-year-olds. The underlying theory incorporates a set of causally interactive endogenous variables that are hypothesized to be driven by the effects of three exogenous variables: parental education, immigrant status and racial/ethnic identity, and parental marital status. The model was run in computer simulation mode, with results comparable to knowledge of school readiness patterns, and in experimental computer simulation mode to evaluate the likely effects of specific interventions by moderating the effects of low parental education and low income on other key variables. Combining the interventions related to cognitive/academic factors, health/nutrition, and family stress with increases in family income had a substantial effect on the relative readiness age of children of parents with low educational attainment and modest improvements for children of non-college graduates. The findings are generally consistent with the literature but emphasize the need for bivariate experimental research that would provide the effect sizes required for more precise systemic analysis.