In order to reduce language-related disparities in educational attainment, teaching standards in many (Western) countries nowadays request teachers of all subjects and grades to focus on their students' academic language development: Especially second language learners and socioeconomically disadvantaged students need continuous and systematic language support (linguistically responsive teaching) in order not to be left behind. To be able to act accordingly, (prospective) teachers need to acquire pedagogical language knowledge and develop positive beliefs about linguistically responsive teaching practices. Our cross-sectional survey among German pre-service teachers (n = 115) shows that - despite positive beliefs towards linguistically responsive teaching - hardly any of the participants had acquired a solid knowledge base in the area of educational linguistics: The majority could not identify a substantial amount of academic language features (known to be challenging especially for second language learners) in a content-specific explanatory text. This ability, however, is the basis for planning and carrying out linguistically responsive lessons. Although latent profile analyses show differences among the participants, many of them did not have opportunities to learn in the area of linguistic diversity during their studies. The results give rise to the question whether and how pedagogical language knowledge could become compulsory in teacher training.