Pupils’ competence and preparedness are assumed to be reflected in their school-leaving scores which are used by employers and further education institutions as signals for selecting appropriate applicants. Schools need a consistent signal of their pupils’ potential success beyond school in order to prepare them appropriately. The introduction of the National Senior Certificate (NSC) in South Africa has led to the admission of students into universities who seem inadequately prepared for tertiary education, especially with regard to their mathematical preparedness. Using a standardised 1st year university test first written in 2006 and repeated in 2009 and 2010, we compare the signalling ability of the NSC school-leaving mathematics scores with the former Higher Grade (HG) in terms of mathematical preparedness. Our findings suggest that the NSC mathematics scores are inflated by around 20–25 percentage points compared to the former HG mathematics scores. However, once deflated, the NSC scores are very good predictors of mathematical preparedness. These results are consistent across the two NSC cohorts which should indicate to schools what the comparable level of mathematical preparedness is across HG and NSC mathematics and allow university admission offices to set more appropriate minimum requirements for university admission.