Oral language enrichment in preschool improves children's language skills: a cluster randomised controlled trial

Oral language skills provide the foundation for formal education, yet many children enter school with language weaknesses. This study evaluated the efficacy of a new language enrichment programme, the Nuffield Early Language Intervention-Preschool (NELI Preschool), delivered to children in the year before they enter formal education.

We conducted a preregistered cluster randomised controlled trial in 65 nursery schools in England (https://doi.org/10.1186/ISRCTN29838552). NELI Preschool consists of a 20-week whole-class language enrichment programme delivered by a teacher each day for 20 min. In addition, children with the weakest language skills in each class are allocated to receive additional targeted support delivered by classroom assistants (whole-class + targeted). The language skills of all children (n = 1,586) in participating classrooms were assessed using the LanguageScreen automated app (https://oxedandassessment.com/languagescreen/). Settings were then randomly allocated to an intervention or control group. The children with the weakest language in each class (whole-class + targeted children n = 438), along with four randomly selected children in each class allocated to the whole-class only programme (n = 288) were individually tested on a range of language measures.

Children receiving NELI Preschool made larger gains than children in the control group on an oral language latent variable (whole-class children d = .26; whole-class + targeted children d = .16).

This study provides good evidence that whole-class intervention delivered in preschool can produce educationally significant improvements in children's language skills. The intervention is scaleable and relatively low cost. These findings have important implications for educational and social policy.