Using Beck, McKeown and Kucan's (2002) three-tiered model as a general framework for vocabulary, this article sheds light on the construct of academic vocabulary and how it might be measured. Using illustrative writing samples of student work of different genres and drawing on corpus based studies, I highlight the distinction between general, high utility academic vocabulary visible in expository mode (Tier 2), and narrative vocabulary (Tier 1) on the one hand; and general, high utility academic vocabulary and literary vocabulary associated with English Language Arts literature-based curriculum (Tier 3). Tier 2 words have consistently correlated with academic achievement across disciplinary boundaries, especially at post-secondary levels. Suggestions are made for policy reform, curriculum, and assessment approaches that will afford more equitable access to post-secondary programs of study for the growing numbers of English language learners across Canada, including in provinces such as Alberta and British Columbia.