Do the Effects of a Preschool Language Intervention Last in the Long Run? A 4-Year Follow-Up Study

Childhood language interventions appear promising for improving children's lives and yielding economic returns. However, few studies have evaluated long-term effects of these interventions. Our study did this using a large, cluster-randomized trial of a preschool intervention for Norwegian children aged 4 to 5 years whose vocabulary was more limited than that of their peers. Results showed that effects on expressive language were maintained at the 7-month follow-up when the children were in first grade and that those with the weakest language skills initially had the largest and most persistent effects. However, 4 years after the intervention, the differences between the intervention and control groups were negligible. Thus, although effects from the preschool language intervention lasted into the first year of elementary school, effects eventually faded and were completely absent in fourth grade. Our findings suggest the need for a sustained approach to language and literacy support, focusing on persistent interventions and high-quality adapted instruction.