Supporting Oral Productivity in the Language of Instruction in Multilingual Preschool Classrooms: Effects of a Multimodal Narrative-Based Intervention

Despite growing evidence showing that oral narrative-based interventions support language learning, research on multilingual classroom contexts remains limited. This study investigates the effectiveness of a nine-session classroom-based multimodal narrative intervention focused on narrative macrostructure in Catalonia, where Catalan serves as the language of instruction but is the non-dominant language for most children. Preschoolers aged 5 to 6 (N = 85) participated in a cluster-randomized controlled trial, and were assigned to either an experimental intervention group receiving the intervention or a control group. Through pre- and post-intervention, all children narrated a wordless animated cartoon. Language productivity (total number of words, TNW) and lexical diversity (number of different words, NDW) in Catalan and Spanish were obtained using CLAN. The results showed that the experimental group significantly outperformed the controls in Catalan TNW post-intervention. NDW raw counts increased significantly pre-to-post, but this effect disappeared after controlling for sample length, indicating that gains in lexical diversity were driven by greater language productivity rather than reflecting independent vocabulary growth. This study provides evidence that a multimodal narrative intervention can foster non-dominant language use in young multilingual learners. More broadly, it offers practical guidance for evidence-based language instruction in multilingual classrooms, where strengthening proficiency in the language of instruction is a key educational goal.