Proficiency with sentence-level features of language is essential for reading comprehension of academic texts, especially for early adolescents who face increasingly complex, discipline-specific texts as they enter upper elementary and middle school. However, little research has been done to explore instruction in sentence-level features. This qualitative case study explores how a sixth-grade social studies teacher developed knowledge of sentence-level features and implemented sentence-level instruction through a professional learning inquiry, as well as how 3 sixth-grade students responded to challenging sentences as a result of this instruction. Findings from thematic analyses of both teacher and student data sources indicate that increased metalinguistic awareness of sentence-level features in the teacher participant was essential to effective, discipline-specific instruction in sentence-level features. Additionally, explicit instruction in sentence-level features led to increased metalinguistic awareness in students, which supported their comprehension of challenging sentences.