This study examined the effect of afternoon classes on Junior Secondary School Students’ Academic Achievement in Mathematics in Mubi North and South Local Government Areas, Adamawa state, Nigeria. The research adopted descriptive survey and quasi experimental research designs. The population for the study was all the junior secondary schools two (JSS 2) in Morning and Afternoon schools in Mubi North and South Local Government Area of Adamawa State. The sample size of the study was 158 students obtained from eighth (8) Junior Secondary Schools through simple random and purposive sampling techniques.  Three research questions were raised and three research hypotheses were formulated to guide the study. Two research instruments were used for data collection: A structured questionnaire titled “Effects of Afternoon Classes on Students Academic Achievement in Mathematics (EACSAAM). The questionnaire has four sections, labeled Section A – d and it was based on a modified 4-point Likert’s scale of strongly agreed, agreed, disagreed and strongly disagreed and Mathematics Achievement Test (MAT) based on the Junior Secondary School curriculum topics. The data collected were analysed using mean, standard deviation and t-test all tested at 0.05 level of significance. Findings from hypotheses one revealed that there is significant effects of time factor on students’ academic performance based on students gender (P<0.05); findings from hypotheses two shows that there is no significant difference between attendance and participation of junior secondary school students in mathematics classes based on age (p>0.05;  finding from hypotheses three revealed  that there is no significant difference among factors hindering students’ readiness and confidence based on Local Government Area (p>0.05). It was recommended that; government should ensure that enough structures are put in place in order to accommodate all students’ in the morning classes; conducive environment needs to be put in place that will encourage and facilitates good learning atmosphere among students; government should enforce close monitoring policy on teachers and students in places where afternoon classes must be introduced.

Keywords: Afternoon classes and Timing, Academic achievement, Mathematics, Readiness, Gender.