"Fadeout" of ECE impacts refers to the diminishing effect sizes of ECE attendance on children's test scores over time, as children age. One possible explanation for fadeout may be that non-participating children actually "catch up" over time, suggesting that the term "convergence" may be more appropriate. Some research suggests that fadeout may occur at a faster rate among children who go on to attend lower-quality schools, although other recent research suggests fadeout occurs at a slower rate in low-achieving schools. The initial achievement gains from Head Start also fadeout at a faster rate for African-American children, who (on average) attend lower-quality schools.
The pattern of (1) initial impacts on test scores, (2) convergence or "fadeout" over time, and (3) significant long-term gains on important adult outcomes was found in evaluations of Perry Preschool, Carolina Abecedarian, Head Start, and even the Tennessee STAR kindergarten class size reduction experiment, indicating that the convergence of test scores and yet long-term gains in adult outcomes is a robust pattern in ECE interventions. In the case of Head Start, children who exhibited the greatest fadeout of ECE impacts actually experienced the largest impacts as adults. Specifically, the children who showed large initial test score gains at ages five and six and diminished impacts at ages 11 and 14 exhibited larger outcomes in adulthood, relative to other Head Start participants, suggesting that initial test score gains may be a better predictor of long-term outcomes than interim test scores. Further, while this study found no difference in test scores during middle childhood, Head Start participants were much less likely to repeat a grade or be diagnosed with a learning disability. This suggests other indicators may be more useful than interim test scores as predictors of long-run impacts. Moreover, these indicators, such as grade retention, often have cost implications themselves.