PROTOCOL: Language interventions for improving the L1 and L2 development of dual language learners in early education and care: A systematic review and meta-analysis.

The aim of the current systematic review and meta-analysis is to comprehensively synthesize the effectiveness of language promotion interventions in early childhood education and care (ECEC) settings on L1 and L2 development of dual language learners (DLLs). We will use the PICOC-Strategy (Population, Intervention, Comparison, Outcome, Context) suggested by Petticrew et al. to frame our research questions.