A Cluster Randomized Controlled Trial Comparing the Efficacy of Pre-School Language Interventions-Building Early Sentences Therapy and an Adapted Derbyshire Language Scheme.

The trial had fewer children than planned. The target was 65 per arm but only 44 children received BEST and 58 received the adapted DLS, so it may have missed real differences between the two, and the authors note that a small sample can inflate the effect sizes found. No untreated control group took part. It was removed during the COVID pandemic because the team judged it unethical to assess children's language without offering intervention, which means it is hard to be sure the adapted DLS achieves more than children would gain from ordinary nursery provision. Children's understanding scores were higher in the BEST group at the start even though the groups were randomly allocated, and the analyses adjusted for this; it is still a sign the two groups were not perfectly matched. The analysis did not account for children being grouped within nurseries, which the authors say would have been the better approach, particularly as some nurseries contributed only one child. The authors also say a multilevel approach would have been preferable. Parents' ratings of communicative participation were too incomplete to use (68 of 102 at the start, dropping to 49 immediately after the intervention), so the participation results rest on the more complete teacher returns. The adapted Derbyshire Language Scheme is not the standard version. Children move faster through the target sentences and get less individualisation, so the results do not tell you how the standard DLS would compare with BEST. The test used to track progress in the adapted DLS arm included some structures that were not taught to every child, which may have understated the progress of that group. Most children came from disadvantaged backgrounds, with 66% living in the most deprived fifth of areas in England, so the findings may not apply to other populations.

The paper states that BEST materials are free to download and that no profits are made by the authors. The adapted Derbyshire Language Scheme manual is available on the DLS website, and one of the authors, M.M., receives royalties from sales of DLS materials purchased there. No funding statement appears in the text supplied.

Do not read the improvements in both groups as proof that either intervention works. The trial had no untreated comparison group, so children's gains could reflect ordinary development or their nursery provision rather than the therapy.