Based on a linguistic ethnographic study of student–teacher classroom interactions, this article sheds light on language norms in a contemporary Danish STX school (upper secondary education, also known as gymnasiums). The analysis reveals that neither classrooms with the explicit teaching of an ‘academic register’ nor classrooms where teachers orient towards a youth norm constitute spaces where students have equal access to perform as good students. Even when students can decode and reproduce the language preferred by the teachers, they do not experience an equal opportunity to conform to this. It is argued that performing linguistically as good and competent students is more complex than just adapting to a specific school norm, as the students have to navigate different teacher’s norms as well as peer norms emphasising authenticity.