There is very strong evidence that participation in high-quality childcare programs enhances "school readiness" and has positive effects on cognitive development outcomes in the short term. In other words, children who have participated in good professional childcare programs, on average, score better on cognitive development tests administered at the start of first grade than children who had no childcare experience.
Some studies have shown that these positive effects can be quite large. However, a significant body of research strongly suggests that these positive impacts of childcare participation tend to diminish or "fade-out" over time. This phenomenon has been found to be particularly pronounced among children from middle- and upper-income families. Bruce Fuller, an American sociologist, in a review of the existing research in the field, states that many studies indicate that for children from economocially comfortable families, the observable positive effects of childcare appear to "fade-out" entirely by the time children enter the fourth grade.
Some experts in the field of child policy dispute the notion that childcare participation effects will, by nature, fade out significantly over time. These researchers often suggest that this phenomenon is partially driven by low-quality learning experiences during primary school. If the educational experiences of children during primary school were of uniformly high quality, these researchers suggest, the tendency of childcare participation effects to fade out over time would be much less strong or nonexistent.
While the concept of "fade-out" is an important one in the are of childcare policy, it is important to note that the tendency of positive childcare participation effects to fade out over time is much less pronounced among children from poor families. While the effect sizes on cognitive development from childcare participation do diminish over time for these children, there is significant evidence that they do not fade out entirely over time, particularly for children who attend high-quality childcare programs. The most famous study of childcare participation on developmental outcomes, the Perry Preschool Project, provides convincing evidence that participation in high-quality childcare programs can have positive impacts on social and cognitive development that last well into adulthood for children from disadvantaged families.