How do we reconcile these findings with the overwhelming body of evidence, gleaned from a half-century of research, which argues that high-quality early childhood development programs, notably including pre-kindergarten, are the smartest investments a community can make?
To make sense of these different conclusions, we need to begin by recognizing that there are different dimensions to early childhood development. It is on the cognitive dimension where the gains made by pre-k children appear to "fade out" by second or third grade. Meanwhile, children who attended pre-kindergarten continue to perform significantly better than their peers on other measures. In particular, children who attended high-quality pre-k are more likely to graduate from high school. They are more likely to go to college, to avoid drugs and crime, and to delay parenting until they are out of their teens.
How does this work? The skills that correlate most closely with lifetime success are social, emotional and behavioral skills. For many children, pre-kindergarten is the first introduction to key concepts like listening carefully to stories, paying attention to directions, and taking turns... Pre-k teaches children ways to solve inter-personal conflicts without hitting or biting. It teaches that stories have beginnings, middles and ends (introducing the idea of cause and effect). It establishes group norms (for example, when someone is talking we listen and don't interrupt). And it teaches children that it's worth paying attention to teachers, because this is how we find out what is going to happen next (a type of speech that research suggests is often absent from low-income homes). On these dimensions (involving higher order, executive, self-regulatory thinking, and involving the pre-frontal cortex in the brain), children who participate in high-quality pre-kindergarten programs continue to do significantly better as they make their way through life than their peers who did not attend pre-k.
In fact, the strongest longitudinal evaluations of the effects of high quality pre-school programs estimate that these programs make good financial sense. Pre-kindergarten programs return upwards of seven dollars for each dollar invested. These gains come in the form of increased individual earnings and tax revenue, and a decreased need for social services and criminal justice services. (For some cohorts of children, for example those who took part in the High Scope / Perry Pre-School Project, the return has proven to be 17 dollars for every dollar invested).
What explains the limitations of the Tennessee Comptroller's report? First, the study only looked at cognitive gains, and it measured these gains on an instrument that doesn’t allow for comparison with other districts across the state or country. Moreover, the study-sample included nochildren from Memphis City Schools (by far the largest and most diverse school district in the state). This matters because the effects of pre-kindergarten are most significant for low-income and minority children.
The research-supported take away for all of us should be that investments in high-quality early childhood programs are among the smartest development dollars that we can spend. This is the logical conclusion to draw from the preponderance of evidence-based evaluations. Moreover, as a community we need to do a better job collecting meaningful data on the risks facing our children, as well as on the particular early childhood experiences that place at-risk children on a pathway to successful school readiness.