Evaluating a Targeted Selective Speech, Language, and Communication Intervention at Scale - Protocol for the 'Happy Talk' Cluster Randomised Controlled Trial.

The overall aim of this clinical trial is to evaluate an at scale version of 'Happy Talk' in a large scale effectiveness study (examining inputs, outputs and outcomes) based on a sample of children from socially disadvantaged areas. Researchers will compare Happy Talk to usual care and children's allocation to the programme will be decided on randomly. The investigators also aim to * complete a pre-trial process evaluation to inform intervention implementation - examining factors which promote parental engagement and partnership between SLTs and educators and incorporating these into SLT training and future rollouts of the programme. * complete a concurrent process evaluation from a realist perspective to examine how the mechanisms underpinning Happy Talk are influenced by the implementation context and therefore what would need to be considered for successful implementation across varied settings. Our SWAT is embedded in this process evaluation and addresses the Trials Methodology Research Network methodological priority questions 1 and 5 https://priorityresearch.ie/priority-one-questions/ * Complete an economic evaluation in which compare the costs and benefits of Happy Talk are compared to standard pre/school care. The study aims to answer the following research questions: When implemented at scale 1. Does 'Happy Talk', a targeted selective intervention focused on increasing parent and early educator responsive interaction, improve language and quality of-life (QoL) outcomes in socially disadvantaged preschool and young school-aged children? 2. Does Happy Talk enhance responsiveness and language promoting behaviours in home and pre/school contexts? 3. What programme features support successful real-world application of 'Happy Talk' including factors which promote parental engagement; partnership between SLTs and educators; and fidelity of implementation? 4. How do contextual factors influence Happy Talk implementation /outcomes? 5. How can trials become part of routine care? 6. Is Happy Talk cost effective compared to usual care? Intervention: The programme is informed by general systems theory and is embedded in the preschools, and homes of socially disadvantaged children with the aim of effecting change in parent and educator behaviour. There are both parent and preschool staff components to the programme.