The quest to contextualise education in Africa has been on-going for a while and many countries have been making efforts towards it. During this time of educational review, conscious efforts should be made to identify problematic levels of some subjects that are dreadful to the learners to pave the way for curriculum re-design for context appropriateness. Mathematics learning in African countries has been a source of concern to all educational stakeholders despite several efforts towards its deconstruction. An examination of performance trend in the subject might reveal at what point the learning started declining and this will suggest intervention towards decolonisation of its content. This study measured the academic performance of pupils from preschool level up to the end of primary education (VI class). A descriptive survey research design was adopted and 720 Primary VI pupils were selected through multistage sampling technique in a state in Nigeria. Primary School Mathematics Performance Record Sheet (PSM_PRS) was used to collect mathematics scores from preschool through Primary VI class. Data were analysed using descriptive statistics and graphs. Pupils started experiencing major declines in mathematics from Primary III class. Results also indicate no significant difference in the class where male and female pupils' performances started declining. Therefore, there is the need to review and contextualise mathematics content from third year in primary/elementary school for effective learning. Activity-based and exploratory strategies using contextual experiences and resources to deliver mathematics lessons were recommended for third year in primary/elementary schools and beyond.