The study investigated the contributions of school-related variables to the academic performance of learners in secondary schools in Bunda District, Mara Tanzania. It specifically assessed the contributions of teacher-related attributes to the academic performance of learners in secondary schools, determined the contributions of learner related factors to learners‟ academic performance in secondary schools. It examined the contributions of the learning environment to learners‟ academic performance in the final examination and examined the contributions of motivational strategies to learners‟ academic performance in secondary schools in Bunda District. The study employed mixed research approaches, whereby the data were gathered using questionnaires and interview guides. The sample size of the study consisted of 4 head of the schools, 4 academic teachers, 23 teachers and 41 students from the selected 4 private secondary schools that lead to 72 respondents. Purposive sampling was used to select the head of schools and academic teachers. The teachers and the students were selected through simple random sampling. The reliability of instruments was tested through the test-rest method with the help of Karl Pearson‟s Product Moment Coefficient of Correlation Formula (r), yielding a reliability coefficient of 0.78. The quantitative data was analyzed statistically and descriptively with the help of Statistical Package for Social Sciences (SPSS) version 20. The qualitative data was analyzed thematically considering patterns and contents. The study revealed that teachers‟ completion of syllabus on time, teachers‟ participation in remedial classes, good teacher-student relationship, good teacher subject mastery, good school management-teachers‟ relationship, teachers‟ salary increment and timely salary payment, rewards, sufficient school infrastructure and teaching facilities including classrooms, books, libraries, laboratories and desks significantly contribute to students‟ academic performance. Basing on the findings, the study established that teachers‟ attributes play an important part in students‟ academic success, learners-related factors are fundamental in attaining high academic performance. In the same vein, the learning environment is very profound in leading to academic achievement. Appreciation through rewarding and incentives enhance work commitment. The study recommended that teachers should undergo in-service training as means of exposing them to new experiences in widening their knowledge. Students should as well be advised instead of expelling or threatening them over low academic performance.