*Names in bold indicate Presenter
Data from the Preschool Curriculum Evaluation Research Study, a random assignment study on the effects preschool curricula, are used in the study. Children in the sample are majority low-income and all are enrolled in center-based child care. Several process quality measures are combined to create a quality composite (ECERS-R, Arnett, and the Teacher Behavioral Rating Scale). Three academic outcomes are examined in the study, vocabulary as measured by the PPVT, and math and reading achievement as measured by the Woodcock-Johnson Psycho-Educational Battery-Revised.
To estimate the effect of child care quality on academic outcomes, an instrumental variables (IV) technique was used (Angrist & Krueger, 2001; Duncan, Morris, & Rodrigues, 2011). The method consists of conducting a Two-Stage Least Squares regression to estimate the endogenous variable’s impact on the outcome variable. In the first stage of the regression site by treatment interactions are used, along with control variables, to predict the process quality composite. The second stage uses the predicted value of quality from the first stage, site, and control variables to predict the academic outcome. We also compare Ordinary Least Squares (OLS) regression results with the IV estimates.
Results for the OLS regressions indicate the process quality composite has a consistently positive and significant effect on vocabulary and reading achievement. No significant effect is found for math achievement. The first stage of the IV analyses is strong as indicated by the large F-statistic (22). The results from the IV analyses show a significant effect of quality on children’s vocabulary and math achievement; however, there is no significant effect of process quality on children’s reading achievement.
Overall, our composite measure of child care process quality was found to significantly affect preschool children’s vocabulary and math achievement. The effects are significant, but small and are similar to the associations found when using OLS. Given the quasi-experimental method used, it was expected that larger effects of process quality would have been found. There has been speculation surrounding the ability of current instruments to provide sufficiently valid measures of child care process quality (Burchinal et al., 2011). Child care quality as presently measured may need to be modified to ensure quality is being measured in a valid way. The findings of the study demonstrate the need to improve the quality measures currently used in early childhood settings, and suggest the need for more rigorous methods in evaluating the effect of child care quality on children’s academic outcomes.