The Effectiveness of a Large-Scale Language and Preliteracy Intervention: The SPELL Randomized Controlled Trial in Denmark

by Dorthe Bleses, Anders Højen, Laura Justice and Philip Dale

19.11.2017 | Mette Vad Andersen


The present article reports results of a real-world effectiveness trial conducted in Denmark with six thousand four hundred eighty-three 3- to 6-year-olds designed to improve children's language and preliteracy skills. Children in 144 child cares were assigned to a control condition or one of three planned variations of a 20-week storybook-based intervention: a base intervention and two enhanced versions featuring extended professional development for educators or a home-based program for parents. Pre- to posttest comparisons revealed a significant impact of all three interventions for preliteracy skills (= .21–.27) but not language skills (d = .04–.16), with little differentiation among the three variations. Fidelity, indexed by number of lessons delivered, was a significant predictor of most outcomes. Implications for real-world research and practice are considered.

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