This qualitative case study focused on the role of cognitive referents in the sense-making process of one teacher as he attempted to change his classroom science assessment. The interpretations identify cultural myths, conceptual metonymys, as well as personally constructed beliefs as referents that constrained change. The teacher's cognitive struggle to make sense of assessment and his role as assessor are linked to conflicting referents he used in varying contexts including day-to-day assessment and summative assessment settings. The results of the study suggest that cognitive referents are important influences in driving how a teacher thinks about assessment and may constrain an individual teacher's implementation of innovative practices. Accordingly, identification of referents such as myths, their associated beliefs, and metonymic conceptual models that teachers use to make sense of their actions is an important first step in developing an understanding of constraints to educational change.