Through Target 4.7 of SDG4 on 'quality education', Agenda 2030 invites governments to take ownership of progress towards ensuring 'Education for Sustainable Development' (ESD) becomes embedded into all levels of education. However, conceptual analysis suggests an ongoing blindspot related to the significance of systems literacy in fostering the many learning outcomes associated with the broader sweep of 'education for the Sustainable Development Goals'. These include (i) the challenges of providing learners with explicit support for key cross-cutting sustainability competencies that integrate cognitive, socio-emotional, and behavioural domains, and (ii) ensuring citizens can move beyond acquiring basic familiarity with elements of systems thinking towards engaging in authentic lifelong learning about 'healthy' and 'problematic' systems, including their prominence and sustainability within society at large. The analysis offered in this 'long form' article helps address such challenges by reviewing key conceptions of systems literacy. It also proposes a model based on weaving together three literacy elements familiar to environmental and sustainability education (ESE): the "functional," "cultural," and "critical." The article concludes with illustrations of the model in terms of its implications for practices of ESE, and a discussion of the model's potential for supporting efforts that further constructive engagement by educators with the SDGs.