German vocabulary sizes of bilingual and monolingual elementary school students in a minority context in Graubünden, Switzerland

Vocabulary size is widely recognized as a strong predictor of language proficiency and academic achievement, yet little research has examined its development in minority-language schooling contexts. This study investigated receptive German vocabulary among 193 fifth- and sixth-grade students in Romansh-medium elementary schools in Graubünden, Switzerland. Using the standardized German Vocabulary Size Test (VST), we analyzed the influence of home language and compared students from Romansh-medium schools with a German-speaking comparison group from a German-medium school (n = 31). The results showed that students with L1 Romansh, L1 German, or bilingual Romansh – German backgrounds in Romansh-medium schools possessed receptive German vocabularies of approximately 4,000–5,000 words, corresponding to CEFR level B2 and sufficient for secondary-level academic learning. In contrast, students whose home languages included neither German nor Romansh scored significantly lower, averaging 1,000–2,000 words – levels insufficient for understanding academic texts. Statistical analyses confirmed a significant effect of home language, while L1 German students in Romansh-medium schools did not differ significantly from their peers in their German-medium comparison group. These findings demonstrate the relative success of Romansh-medium education in fostering German academic vocabulary, while underscoring the urgent need for targeted German language support for students from other linguistic backgrounds.