This paper looks into the case of a school in Macao nominated as the first (and so far the only) China-Canada-United States English Immersion (CCUEI) centre in the Macao Special Administrative Region (Macao SAR) China for the experimentation and application of English immersion instruction (EI) in the K1-3 and Primary 1-2 classes. Drawing on Krashen's Input Hypothesis (1982) and Cummins' (2000) framework of instruction for language learning and academic achievement in the formal school context, the authors report their observations by analyzing the data collected from school teachers and participation in classes and by reflecting on their experiences, and suggest improvement that can be made to teachers' linguistic and communicative competence, in terms of quantity and quality of comprehensible input and expected output, and thus the sustainability of English immersion classrooms in a Chinese context.