This study uses data from a comprehensive meta-analytic database of early childhood education (ECE) program evaluations published between 1960 and 2007 in the United States to examine the incremental effects of adding enhancement program components to ECE programs on children's cognitive abilities, pre-academic skills, behavioral, health, and socio-emotional outcomes. Preschool enhancement programs include parenting programs, skill-based curricula, and teacher professional development programming. Our findings suggest that the addition of parent programs and skill-based curricula to ECE programs can result in improvements to a range of children's ECE outcomes leading to better school readiness. We found no differences in the impacts of ECE programs with or without additional professional development enhancements. Practice or Policy: Designing fully-developed parent programs by explicitly targeting parents, developing academically focused and skill-based curricula, and providing additional teacher professional development enhancements to existing ECE programs can have a substantial impact on a range of children's ECE outcomes leading to better school readiness. Further research is needed in order to determine what conditions are essential to enhancement program success as well as what conditions have negligible effects on or inhibit children's school readiness. (author abstract)