In South Africa many school-leavers are underprepared for higher education, especially in academic literacies, including numeracy. It is important for higher education to identify the students most vulnerable to failure in coping with the numeracy demands of the curriculum, so that resources available for interventions can be most fairly used. To this end, we seek to answer the question: 'What is the relationship between students' academic numeracy and their mathematical and language competence.' We investigate the relationship between students' academic numeracy scores (on a test reflecting the expectations of higher education) and their writing of four school-leaving examinations that reflect most directly mathematical competence and language ability. In a sample of 7464 students, only 13% had numeracy test scores that were classified as proficient, almost all of whom had studied "Mathematics" and "English Home Language." Almost 90% of those who took "Mathematical Literacy" and "English First Additional Language" achieved scores in the lowest category. Comparing the test score distributions of groups of students defined in terms of the mathematics and language school subject combinations, reveals that mathematics competence and language ability are equally related to students' academic numeracy. The results indicate the need for curriculum reforms in schools and in higher education. Ideally, development of students' academic numeracy should be infused in the teaching of the disciplinary discourses. The effectiveness of interventions intended to improve academic numeracy will be enhanced if they focus not only on quantitative competence but also on language development.