The traditional transmission-based school curriculum in South Africa has been replaced by an outcomes-based school curriculum since 1998. In this article we report on a comparative study on the mathematical knowledge and skills of two cohorts of first-year students: the last cohort to be exposed to a transmission curriculum in Grades 10-12 and the first cohort to complete their entire school career according to an outcomes-based curriculum. The performances of the two cohorts were analysed in terms of procedural, proceptual and conceptual knowledge constructs, as well as topic areas of school mathematics. A t-test statistical analysis of the results of a mathematics diagnostic test was used in the analysis. A statistically significant difference with a small effect size was established for procedural knowledge, indicating that the outcomes-based education cohort has poorer algebraic skills. Statistically significant differences with a small to medium effect were obtained in the question-by-question comparison of topic areas, indicating a possible improvement in the conceptual knowledge of students of the outcomes-based education cohort.