A case study presented here is an investigation into whether time of day for instruction has an effect on students' academic achievement in Mathematics, Science, Biology and English at school certificate level by focusing on the grades candidates obtained after sitting for national examinations. The focus is primarily on 33 randomly selected morning and afternoon pupils at Chibote Girls Secondary School. We hypothesized that morning pupils perform better than afternoon pupils owing to the fact that pupils who learn in the morning have a higher retention rate as compared to those who learn in the afternoon when the temperature is quite high. This hypothesis was tested using a non-parametric Mann-Whitney U test which showed that there was no statistically significant difference across the categories of the two learning modes in Mathematics, Science and English. Furthermore, the same results were analysed through a component plot in rotated space (factor analysis) which showed a significant difference in students' performance between Mathematics and English for both learning modes. Descriptive statistics were computed and the general picture was that pupils performed poorly in all the four subjects with mathematics placed at the tail and English in the lead.