This study aimed to provide evidence for continuing the innovation of writing instruction in Grades 7-12 of Chilean public schools. Teachers' beliefs influence their curricular interpretations; therefore, these beliefs play a key role when aiming for educational innovation. Hence, we investigated the relations between Language teachers’ current practices of implementing the national curriculum and their beliefs regarding five paradigms of Language instruction. While beliefs on writing instruction are possibly embedded in beliefs on the broader topic of Language instruction, we took this broader category into account. We obtained 182 completed surveys from teachers of all Chilean regions (response rate: 47%). Teachers reported a rather strong adherence to four curricular paradigms both in terms of practices and beliefs, while the fifth, the communicative paradigm, demonstrated a low level of adherence. The strength of the implementation of teachers´ practices of writing instruction seemed to be related to teachers´ beliefs, about writing and more general aspects as well. The results suggest that policymakers must focus public efforts on reinforcing teachers’ beliefs regarding writing instruction, especially regarding communicative writing and on the connections between the five paradigms. In addition, we recommend that public efforts prioritize improvements in Grades 9-12 over Grades 7-8.