This paper investigates the development of academic language proficiency through immersion in middle school programmes in Hong Kong and Xi'an. The study reveals that in both contexts students have exposure to complex academic language through teacher talk and textbooks; however, there is not sufficient support for students' academic language use in writing. The paper discusses the possible causes and suggests how students can be helped to develop better academic language proficiency in these immersion contexts. (Contains 2 notes, 7 extracts, and 8 tables.)