Abstract
Abstract This systematic review examines scaffolding practices in science instruction within Content and Language Integrated Learning (CLIL) environments, where English as a foreign language is the medium of instruction (L2). Adopting PRISMA guidelines, 1,052 records were identified, of which 19 were eligible for inclusion. Our analysis shows the essentiality of rediscursification (modifying instructional discourse) and transsemiotization (combining semiotic resources to enhance the message). It also shows variability in the discourse around translanguaging (the fluid use of languages) across contexts, and that preferences for scaffolding practices are shaped by cultural dispositions. The majority of the studies were non-experimental and focused on vocabulary, with only a minority applying heuristics designed for integrating content and language. We raise the question whether some multimodal resources and students’ first languages truly promote science literacy in CLIL. Finally, we provide research-based implications for science CLIL teachers and trainers to support deeper learning in the L2 science classroom.