Title: Does having a preschool teacher with a bachelor's degree matter for children's development outcomes?
Description: As part of the complex but intriguing question of what defines a highly qualified early childhood teacher (Kagan, Kauerz, & Tarrant, 2008), there has been a heated policy debate over whether to make a bachelor's degree (B.A.) the minimum education requirement for preschools' lead teachers in publicly funded programs (Zigler, Gilliam, & Barnett, 2011). A mixed and non-causal research base of the effect of a B.A. on preschool-teacher performance and child development outcomes is a partial source of the controversy (Kelley & Camilli, 2007; Early et al., 2007). Particularly, no experimental or quasi-experimental studies have been conducted for this topic (Barnett, 2011b). To fulfill the need for better causal inference, this dissertation first uses a nationally representative sample of American children born in 2001 who attended a preschool in 2005, to estimate the effect of having a lead teacher with a B.A. in preschool on the children's development outcomes assessed at aged 4, based on data from the Early Childhood Longitudinal Survey, Birth Cohort (ECLS-B).

The term preschool is an umbrella term for all types of center-based programs. Based on three rigorous quantitative methods, including ordinary least squares with rich controls (OLS with rich controls) and two quasi-experimental methods (propensity score matching (PSM) and instrumental variables (IV)), this study finds: (1) In the model of OLS with rich controls, four of the eight comprehensive child development outcome constructs at age 4 are affected by teachers' B.A. status. Children with B.A. teachers are shown to exhibit higher early reading and math skills and fewer parent-reported internalizing behavior problems than children with non-B.A. teachers. No effects are found for story-telling skills, color recognition, parent-reported externalizing behavior problems or approaches to learning skills. Yet the children in the treatment group are reported by parents to have lower social competence. In PSM, B.A. positively predicts math skills and negatively affects social competence. In the IV estimates, a B.A. effect is only found for reducing parent-reported externalizing behavior.

Comparatively, the PSM and IV estimates tend to be less statistically significant than the OLS estimates. This difference may be attributed to either bias or heterogeneity, given that the PSM and IV estimate may have removed some endogeneity of the treatment in a better way than OLS but they cannot represent the whole sample---the PSM estimate is for those matched and the IV estimate is only local to compliers. Further, when comparing teachers who have just a B.A. (as opposed to a B.A. or higher) with teachers who have an associate's degree (A.A.), the B.A. is found to have fewer statistically significant effects in the model of OLS with rich controls. Significant effects are found for two outcomes: Having a teacher with a B.A. increases math skills and reduces internalizing behavior problems. (2) There has not been much evidence of differential effects by preschool type, and the B.A. effects are no larger for children from low socioeconomic status (SES) families. Neither does the specialized education in early childhood education (ECE), as measured by whether a teacher has a degree in ECE or a related field and the number of college courses in ECE, interplay with the B.A. effect. (3) The supplemental analysis that uses two steps regression to link B.A., teacher-child interactions and child outcomes also returns some interesting findings.

The treatment B.A. is found to increase the frequency of several classroom activities and the quality of teacher-child interactions (i.e., being more sensitive, less harsh, less detached and less permissive); but the two steps of the analysis only provide slight evidence for the mediating role of teacher-child interactions. Overall, there is some positive evidence of B.A. effects on children's early reading, math, the reduction of parent-reported internalizing behavior problems, the reduction of internalizing behavior problems and positive teacher behavior for the center-attending children in the ECLS-B dataset. Still, the evidence is not very strong given the inconsistency of findings across models and the negative effect of B.A. on parent-reported social competence. Such findings identified by rigorous methods in this study speak directly to the B.A. debate by adding a new piece of empirical information for a new generation of children and teachers; it adds some positive evidence to the pro side.

Still, for future research and practice that aim to elevate quality, a full picture of cost-effectiveness and cost-benefit of the B.A. threshold policy is recommended and other teacher quality components should be considered.