Propensity score analysis is a statistical method that balances pre-existing differences across treatment conditions achieving a similar condition as randomization and thus, allowing the estimation of causal effects in non-randomized experimental designs. The four stages in propensity score analysis are (1) propensity score estimation, (2)…

We present evidence that the positive relationship between kindergarten entrance age and school achievement primarily reflects skill accumulation prior to kindergarten, rather than a heightened ability to learn in school among older children. The association between achievement test scores and entrance age appears during the first months of…

Low-achieving students in many school districts are retained in a grade in order to allow them to gain the academic or social skills that teachers believe are necessary to succeed academically. This practice is highly controversial, with many researchers claiming that it leads to higher dropout rates although selection issues have complicated…