A randomised controlled trial, conducted by Silke Fricke and colleagues, looked at the effect of an oral language intervention and compared the extent to which a 30-week programme beginning in nursery and continuing for 20 weeks in Reception was more effective than delivering a 20-week programme starting in Reception.
Children from 34 nurseries in the UK were randomly allocated to a 30-week intervention (n= 132), a 20-week intervention (n=133), or an untreated waiting control group (n=129). Allocation was minimized for gender, age and verbal skills. The children in the 30-week intervention group received the Nuffield Early Language Intervention programme for 10 weeks in nursery and continued for 20 weeks in Reception. The 20-week intervention group received only the final 20 weeks of the intervention, beginning when they entered primary school. The control group received their usual schooling.
Children in both the 20- and 30-week programme intervention groups showed greater improvement in oral language skills on measures including the CELF Expressive Vocabulary and CELF Sentence Structure subtests, and the Information Score from the Renfrew Action Picture Test, compared to children in the control group (effect size for the 20-week programme = +0.21; effect size for the 30-week programme = +0.30). However, there was no evidence to suggest that either programme improved early literacy or reading comprehension skills.
Source: The efficacy of early language intervention in mainstream school settings: a randomized controlled trial (October 2017), Journal of Child Psychology and Psychiatry, 58. doi:10.1111/jcpp.12737