ABSTRACT This study was aimed at investigating the effect of teacher-student ratio on teacher‟s job performance: A case study of ward secondary schools in Nyamagana District. The major purpose of the study was to examine the trend of Teacher-Student Ratio in ward secondary schools, to establish challenges that affect teacher‟s performance caused by teachers student ratio in ward secondary schools; to establish the relationship between teacher-student ratio and performance of students in form four National examinations in ward secondary schools and, to find out the level of motivation on teacher‟s job performance due to the present teacher student ratio in ward secondary schools. The case study research design was used in this study. Data was obtained through questionnaires, interviews and documentary review. Data were analyzed by descriptive statistics specifically; frequency and percentages with the help of Statistical Analysis Pragrammes which are Microsoft office word and Microsoft office excel 2007. The findings showed that, most of the ward secondary schools had higher teacher-student ratios, and large class sizes. The higher teacher student ratio affected teachers fail to accomplish activities like managing students in classrooms, provision of adequate tests, assignments, practical, guidance and counseling, and used teacher-centered teaching method. However, failure to appreciate effort exerted in terms of compensation demotivated teachers in executing their responsibilities thus led to poor performance of students in ward secondary schools. The research recommended that decision makers in the MOEVT, for the ward ordinary level secondary schools education aspiring to excellence must ensure that adequate number of quality teachers is recruited to serve the students enrolled in secondary schools