The objective of this study is to evaluate the internal performance of education systems in sub-Saharan Africa. The choice of the academic performance of student work in reading and mathematics (defined as the ratio between the score obtained in a subject and the investment in learning that subject) as the approach to internal performance constitutes the originality of this research. Based on 2019 data from the Confemen Programme for the Analysis of Educational Systems (PASEC) covering 14 countries in sub-Saharan Africa, the choice of bivariate modelling allows the hierarchical structure of the data to be taken into account and the performance of schoolwork in reading and mathematics to be treated simultaneously. The results show that the influence of learner and school characteristics on performance in reading and mathematics converges. Nevertheless, certain personal attributes of the pupils or certain aspects specific to the school attended generate differentiated impacts depending on the subject considered. Sensitivity and robustness analyses confirm the stability of the results, offering avenues for understanding and improving students' academic performance.