Variability in education systems is a given. Variability has at once positive and negative implications for the main goal of education which is accelerating learning across diverse contexts and for all learners. In this article, we explain and employ a tight-loose framing to understand the scope for variability within an education system. A tight-loose framing directs attention to the interplay of prescription/accountability and autonomy. This framing is yet to be fully explored as a way of understanding and exploiting variability across the curriculum-pedagogy-assessment dynamic within a high-stakes assessment context. High-stake assessment has particular susceptibilities to variability because of its consequences for stakeholders and implications for accountability across the various levels of the education system. We illustrate the tight-loose framing through a case study from New Zealand of a teacher and her class of Year 12 science learners who were working towards the national senior secondary school exit qualification. The teacher was trialling a new General Science course that emphasised inquiry. Observation and interview data were collected over the course of the school year. We analyse the contours of variability across levels of the national curriculum and assessment policy, school agendas, teacher pedagogy, and student decision-making and experiences. Our findings show that teachers and students made trade-offs according to felt accountabilities and priorities within the tightness and looseness of their education context, as they perceived and experienced it. Our proposition is that a multi-level tight-loose framing provides a new and different insight into how policies, philosophies and practices interact under high-stakes conditions to affect outcomes for learners.