Comparing the Applicability of Three Different Speech Therapy Service Delivery Models for Preschoolers with Intellectual Disability: A Single-Blind Randomized Controlled Trial

Many Speech and language pathologists (SLPs) are employed by Iran’s Ministry of Education, with services traditionally delivered through a pull-out model. However, alternative service delivery models (SDMs), such as classroom-based and consultant approaches, are also available for SLPs working in schools. While the advantages of these approaches have been established in other countries, their effectiveness in the Iranian context remains unexplored. This study sought to determine which SDM is more effective in enhancing language skills among Persian-speaking children with intellectual disability (ID) in Iran. This study employed a single-blind, randomized, controlled trial design. Twenty-one preschoolers, with a mental age of approximately 4:6, were randomly assigned to one of three groups (pull-out, classroom-based, and consultant) to receive speech therapy services. Language skills of all students were assessed by an experienced speech therapist using the Persian version of Test of Language Development-Persian:3 (TOLD-P:3), which has demonstrated favorable content validity and acceptable reliability. The language age of students on core subtests and their compositions were compared using the Kruskal-Wallis test.Analyzing language areas and compositions revealed that speech therapy was effective across all delivery service models. However, notable changes were observed in students under the consultant model, particularly in their "Grammatical completion" score (p = 0.011). Additionally, significant improvements were noted in four other composition scores: 'spoken language' (p = 0.05), 'organizing' (p = 0.009), 'speaking' (p = 0.017), and 'syntax' (p = 0.055). The findings of this study demonstrate that speech therapy, irrespective of the service delivery models (SDMs), effectively improves language skills in children with ID. However, the consultant model emerged as the most effective among the three models (pull-out, classroom-based, and consultant) for children with ID.