<p>Research consistently demonstrates that children with internalizing problems (IP) face distinct challenges in academic settings as well as in social interactions with teachers and peers. Consequently, investigating IP within the school context is crucial. Despite the existence of a variety of assessment approaches, few studies have compared them in school-based IP research. This scoping review, therefore, examined the consistency of the conceptualizations of IP and the research topics addressed within school-based studies on IP. Studies were identified through a systematic literature search of ERIC, Psyndex/PsycINFO, and PubMed. In addition, we reviewed frequently used instruments by analyzing the items used to operationalize IP in terms of symptoms and consideration of the school context. A total of 61 studies were included. Our findings indicate that definitions of IP predominantly included anxiety and depression. However, approximately one-third of the analyzed studies did not provide an explicit definition. The majority of studies focused primarily on social outcomes, particularly examining interactions with peers. The analyzed studies differed widely in terms of the instruments used and the informant perspectives considered. Across instruments, interpersonal problems, negative self-image, and specific anxiety were the symptoms most frequently included, but large variability between instruments raises the question whether assessment of IP is always comparable in different studies. Furthermore, only a few of the analyzed instruments adequately considered the school context within their items. This heterogeneity poses significant challenges for comparing study results and underscores the necessity for more standardized approaches to support early identification and intervention in schools.</p>