These include, for example, the achievement gap between low- and high-status groups, differences in access to schooling, and the segregation of students into different types of schools and school programmes. Willms (2011) argued in the OECD's Education al a Glance (OECD, 2011), that equality and equity should be defined as separate concepts and measured with a consistent approach. Equality is therefore measured by the differences among groups in the distribution of Prosperity Outcomes, which are performance, attainment, health and well-being, and attitudes towards school and learning.