Effectiveness of language‐sensitive subject teaching: Heterogeneity and quality of the evidence and implications for future research

Abstract We report and appraise the heterogeneity and quality of 53 primary studies included in a systematic review project on the effectiveness of language‐sensitive subject teaching in primary and secondary education to provide a comprehensive overview of the research field and to give detailed recommendations for future research. We followed a systematic review process adhering to existing guidelines and procedures to define inclusion and quality criteria for experimental, quasi‐experimental and observational studies published since 1990 in English and German. We performed an extensive search, screened on titles, abstracts and full texts, and found 55 studies to meet the inclusion criteria. Out of these studies, 53 studies fulfilled the quality criteria (assessment of internal validity) and were included in the review. Most of the studies show that students taught with language‐sensitive approaches achieve the same or better results than students taught using non‐language‐sensitive approaches for at least one content or language learning outcome (for the results of the narrative synthesis, see Höfler et al., Zeitschrift für Erziehungswissenschaft , 2023, 27, 449). Here, we examine in detail the characteristics of the included studies in terms of the heterogeneity of populations, interventions, outcomes, and study designs and provide arguments for a careful interpretation of the review results. We argue that limited methodological and reporting quality introduce risk of bias to varying degrees. We address methodological issues and gaps in research and present our detailed recommendations for future work informed by our findings. Context and implications Rationale for this study: This paper systematises the heterogeneity, quality and scope of the studies on the effectiveness of language‐sensitive teaching and gives detailed recommendations for future research. Why the new findings matter: Our findings help shape the trajectory of research on language‐sensitive subject teaching. Implications for researchers and policy makers: This article describes the state of knowledge concerning the effectiveness of language‐sensitive subject teaching. Our results provide educators and educational researchers with a systematised overview of the tested approaches and their effect on different learning outcomes. Based on our assessment of the study quality and the transferability of the results, we point out research gaps and offer detailed recommendations to help researchers design new research projects. Our results will also aid policy makers in deciding what evidence to consider in the context of evidence‐based practice as well as in the formulation of future funding directives.