Ensembles such as rock and pop bands are places of exciting creativity and intense, enjoyable music making for young people. A recent review of New Zealand's secondary school qualification, the National Certificates of Educational Achievement (NCEA), has resulted in a new composition assessment of individuals' achievement in groups. An analysis of literature suggests that assessing the achievement of individuals in groups is complex and potentially problematic for novices. This is supported by the findings of an investigation into teacher and student experiences of the new NCEA assessment. In particular, the assessment of an individual's contribution to a collaborative compositional process was found to present significant challenges to pedagogical and assessment practice.