This article examines collaborative writing in schools by systematically reviewing peer-reviewed and empirical articles published in English in scientific journals between 1986 and 2020. Drawing on scoping review methodology and using the typology of collaborative writing, 107 studies on collaborative writing in first-language school contexts (primary to upper secondary) were analyzed. The research gaps are related to school contexts and theoretical underpinnings. Most studies are performed with a sociocognitive, sociocultural or constructivistic theoretical foundation. Therefore, we recommend future research to be conducted with more theoretical diversity and in higher school grades (e.g., upper secondary). Further, most studies analyze the drafting process, whereas the brainstorming and outlining activities are underresearched. Technological advances aside, few articles explicitly study collaborative writing related to technology. In addition to these research gaps, we recommend that longitudinal studies be conducted.