Despite several education policies related to the Sustainable Development Goals, educational inequalities persist at the primary school level in Cameroon. However, little is known on students' circumstances and efforts in an attempt to reduce these inequalities. The aim of this paper therefore is to analyse inequality of opportunity in Cameroon's primary education sector. Using the 2014 and 2019 PASEC databases, we decompose students' reading and mathematics test scores based on Shapley and non-parametric approaches to assess the role of household, school and environmental circumstances. Results show that inequality of opportunity contributes between 38.1 % and 46.3 % of total inequality for between 2014 and 2019 in test scores. Interestingly, school factors like school type, location, resources, and class size, have a bigger impact than students' family background. Policies to improve school conditions should focus on rural and under-resourced areas in terms of educational materials, while improving school inspections and reducing class sizes may be more effective in reducing educational inequalities.