Data from sub-Saharan Africa show that many students leave school without the skills they need. To address this issue, it is important to understand what factors influence learning. According to the Heyneman and Loxley effect established in 1983, in low income countries school quality influences how much students learn more than those students' backgrounds. Recent research suggests that this influential conclusion no longer holds, without discounting the possibility that this trend could still be observed in very-low income countries. The present work investigates this possibility by using the PASEC dataset, which includes ten countries in West- and Central Africa. Improving on Heyneman and Loxley's methodology by using general dominance analysis, this article finds no support for the 'Heyneman-Loxley Effect'. Both school resource and student background account for around half of the explained variance in learning. This suggests that both family- and school-related factors are important sources of inequality of opportunity in low-income contexts.