There is global recognition of the need to teach and assess complex competencies, which are often referred to as twenty-first century or work-ready knowledge and skills. While several assessment frameworks have been co-developed by researchers and teachers to assess competencies in schools, little is known about how these frameworks are shaped, both in product and process, by the active participation of other key stakeholders. This study, therefore, examined the co-construction of a competency-based assessment framework, incorporating the perspectives of teachers, students, and industry partners from an Australian secondary school community. Our findings reveal that the students confidently designed, articulated and justified the framework and then presented this to the adult participants, despite existing power dynamics. In addition, the students were able to navigate the co-construction process through acts of leadership and the use of questioning techniques, unmasking the opportunities for student leadership and voice within the design of assessment frameworks. We argue that the co-construction of assessment frameworks, involving a range of stakeholders, allows for workplace competencies to reflect school priorities and structures while also addressing the realities of the workplace and the needs, capabilities and imagined futures of students.