Argumentation is considered crucial in numerous disciplines. However, it is unclear whether argumentation is understood in comparable ways across disciplines. This study examined how students perceive argumentation in science and language lessons, and investigated beliefs about the relevance of discourse and facts. Data from 3,258 high school students were analyzed with multigroup-multilevel-structural-equation-modeling to disentangle whether or not differences across disciplines exist and the extent to which variation in beliefs can be explained by gender and school track. Results showed that students perceived facts as highly relevant for science lessons, whereas discursive characteristics were considered significantly less important. Discourse played a central role in language. These differences were independent of students' gender, but school track predicted the differences in beliefs significantly.