Although racial segregation has been abolished for 18 years now, schools which served predominantly White students under apartheid remain functional, while those which served Black students remain dysfunctional and unable to impart the necessary numeracy and literacy skills students should be acquiring by this level. The present study provides an overview of this dualistic nature of the primary education system in South Africa, with special attention paid to the bimodality of student performance. It argues that there are in fact two different education systems in South Africa and thus two different data-generating processes. These two sub-systems can be seen when splitting student performance by former-department, language, or socioeconomic...