Implementation takes time: Reduction of literacy problems in schools implementing an early-literacy intervention

Early-literacy interventions might prevent reading problems in the long term, but effects are rarely examined at scale. In this study, we examined whether the large-scale implementation of the Dutch early-literacy intervention Build! reduced the percentage of readers with difficulties and improved mean reading skills at the school level. Transfer effects to spelling and reading comprehension were also examined. Over the course of 6 years, schools not implementing Build! (61–126 schools, depending on the outcome measure) were compared to 72 to 145 schools that introduced Build! during the project. Per year, intervention schools were modeled as using or not using the intervention. Using difference-in-difference models, we examined changes in literacy skills from the moment the intervention was introduced. Findings indicated that there was no immediate effect of the intervention. However, after the intervention had been used for 2 years, the percentage of children with difficulties in reading, spelling, and reading comprehension started to decrease and the mean reading and spelling ability increased. Results suggest that large-scale evaluations of interventions should be continued for several years, as effects might show several years after the implementation of the intervention.