The purpose of this study was to identify factors that affect academic achievement of students in Gata High School at Sigimo Woreda Jimma Zone Oromiya region. To identify these factors, questionnaire and interview were prepared for the students, parents, school administrative and teachers. Through this, the study has been able to establish issues that are particular to Gata High School. These factors attributed to teachers, school environmental, parents and the students were primarily responsible for the low academic achievement of the pupils. The school environmental factors identified include limited number of teachers with high academic qualification, inadequate teaching and learning materials, and misuse of contact hours with students. The teacher factors that were found to contribute to the low academic performance were incidences of lateness to school and absenteeism, inability to complete the syllabi and inadequate homework assigned to pupils. The student characteristics found significant were incidences of lateness to school and absenteeism, lack of assistance with studies at home and use of local language in the classroom. Home conditions or parental support variables causing pupils to perform poorly academically were their inability to provide textbooks and supplementary readers, low level of interaction with childrenâ€™s teachers, and low involvement in the Parent Teacher Association. The study has practical significance as it sheds light on the factors affecting the low academic achievement of the students in Gata High School and for decision making to improve their academic performance. It was recommended among others that there is the need to improve parentsâ€™ attitudes, intensify supervision of teachers and institute incentive packages, sensitize and motivate the pupils, recognize individual differences in education and encourage guidance and counseling services for students