Early language screening and intervention can be delivered successfully at scale: evidence from a cluster randomized controlled trial.

Background: It is well established that oral language skills provide a critical foundation for formal education. This study evaluated the effectiveness of the Nuffield Early Language Intervention (NELI) programme in ameliorating language difficulties in the first year of school when delivered at scale.

Methods: We conducted a cluster randomized controlled trial (RCT) in 193 primary schools (containing 238 Reception classrooms). Schools were randomly allocated to either a 20-week oral language intervention or a business-as-usual control group. All classes (N = 5,879 children) in participating schools were screened by school staff using an automated App to assess children's oral language skills. Screening identified 1,173 children as eligible for language intervention: schools containing 571 of these children were allocated to the control group and 569 to the intervention group.

Results: Children receiving the NELI programme made significantly larger gains than the business-as-usual control group on a latent variable reflecting standardized measures of language ability (d = .26) and on the school-administered automated assessment of receptive and expressive language skills (d = .32). The effects of intervention did not vary as a function of home language background or gender.

Conclusions: This study provides strong evidence for the effectiveness of a school-based language intervention programme (NELI) delivered at scale. These findings demonstrate that language difficulties can be identified by school-based testing and ameliorated by a TA delivered intervention; this has important implications for educational and social policy.