This position paper examines the phenomenon of the McNamara Fallacy to analyse flawed conceptions of "success" in mathematics learning, normalised assessment structures and their implications for mathematics education. The established presence of the McNamara Fallacy and the ramifications of this statistical fallacy provide a foundation to demonstrate its existence and parallels within mathematics education, including NAPLAN and other common assessment structures. Viewing such assessments through the lens of the McNamara Fallacy allows educators to recognise, explain, and potentially address their negative consequences.