The New Zealand education system is culturally diverse and is guided by the principles of the Treaty of Waitangi to produce equitable outcomes for Maori students. The reporting of national educational outcomes is broken down by ethnicity to monitor educational performance of different ethnic groups and to identify ethnic disparities. The Ministry of Education and the New Zealand Qualification Authority use a system of ethnic priority ranking to expedite the statistical analysis of educational outcomes for students who identify themselves as belonging to more than one ethnic group. This approach may inadvertently distort reported ethnic disparities in key outcomes of our education system. The study investigates the impact of the method of ethnic labelling on reported national outcomes of the education system and recommends an alternative weighted ethnicity approach. Questions are raised about the appropriateness of the current ethnic classifications.