This thesis explores how the turn towards ‘21st century learning’ might influence senior secondary science education in the context of high stakes summative assessment in Aotearoa New Zealand. Significant in the set of assumptions and ideals associated with 21st century learning is the expectation that learning is more personalised to address and allow for diverse student needs and interests. However, in the reality of classroom life, a question remains as to if and how 21st century ideals might translate into practice. A social constructionist theoretical orientation directed attention to the way 21st century learning as a discourse constructs certain conditions of possibility for teaching and learning. In turn, these conditions were viewed as shaping different possibilities for teacher and student positions and identities. Four macro-level elements of curriculum, assessment, physical spaces, and digital technologies were used to frame an examination of the ways in which the discourse of 21st century learning might play out in senior secondary science. Interpretations of science as a key learning area in the New Zealand curriculum (NZC) and the National Certificate of Educational Achievement (NCEA) as the New Zealand secondary school exit qualification provided the contexts for elements of curriculum and assessment. Research was conducted in schools designed as open, shared, flexible learning spaces (FLS), incorporating wired and wireless technologies. This provided the context for the elements of physical space and digital technologies. The research was designed in two phases. In phase one, three case studies were undertaken to ask: What does senior secondary science learning look like in FLS schools when teachers and students are focussed on NCEA assessment? In phase two, three cycles of collaborative action research were undertaken over eight months with one teacher and her year 12 science class to explore: What could senior science learning look like? Qualitative data generated from interview and participant observation in both phases was analysed using thematic analysis to understand what science learning looked like or could look like. Social constructionist ideas of discourse, positioning, and identity were used to theorise and explore the overarching research question of how the discourse of 21st century learning might influence notions of senior secondary science to reposition teachers and learners of science. Findings show how the multifaceted identities taken up by teachers and students were shaped by the pedagogical possibilities created and available within the dynamic interplay between the four elements. Teachers and students could be seen to be positioned by and to position themselves within discourses of 21st century learning as personalisation and choice, and traditional science schooling, in action and tension. Some aspects of NCEA assessment acted to strengthen the traditional science schooling discourse which foregrounds science as knowledge-based and supports identities of teacher-expert as transmitters of knowledge. Other aspects of NCEA provided openings in line with science as inquiry as advocated in the NZC. Some aspects of FLS environments did not support some teachers’ view of traditionally effective approaches to science teaching and practical work. However, the affordances of digital technologies and the fluidity and social flow of flexible spaces enhanced possibilities for many forms of learning choices. Flexible spaces supported team teaching of larger groups and collaboration of teachers across science disciplines. Teachers responded to these openings by scaffolding different types of learning choices for diverse senior students in what, why, where, how, and with whom to learn, at different levels of openness in science inquiry. However, some students did not take up the full scope of the opportunities offered, especially where these were in tension with students’ ideas of how best to be successful in terms of achieving credits in NCEA. Findings reinforce the importance of the teacher’s role in scaffolding student autonomy to make choices and to achieve in student-directed inquiries. Overall, and in spite of the challenges and tensions that teachers and students faced, this research identifies opportunities for broadening the definition of ‘good’ science teacher and learner to include the offering and uptake of a range of learning choices in senior science inquiry as part of high stakes assessment. This research contributes insights in the form of situated stories of the struggles and achievements of teachers and students: what was happening and what did happen as they were positioned and as they acted to reposition themselves to take on different science teacher and learner identities in contexts of high stakes NCEA assessment in 21st century FLS environments. A range of implications for learning space design, curriculum and assessment policy, and directions for further research into science inquiry and digital pedagogies are outlined.