The purpose of this study was to assess the school leadership effectiveness on students’ academic achievement in terms of leaders’ instructional leadership roles and leadership styles and to see factors affecting their effectiveness in the secondary schools of Jardaga Jarte woreda. The study employed a descriptive survey research design and quantitative and qualitative research methods. Among 4 secondary school in the woreda, 4 were selected by available sampling technique and all of the (4) secondary schools in this woreda were included as a sample. Data for the study were collected through questionnaires, interviews, and document analyses. Questionnaires were prepared and administered to 43 teachers selected by using available sampling techniques and 25 school leaders. All principals were interviewed and the analyses of necessary documents were made in all sample secondary schools. The data collected were analyzed by using percentages, means, and weighted means. The data gathered through open ended questions, interviews and document analyses were analyzed qualitatively through narration for the purpose of triangulation. Finally, the findings of this study revealed that there is an insignificant school leadership roles played as an instructional leaders for students’ academic achievement; moderate commitment of school leadership to influence students’ achievement; poor performance of students’ academic achievement and moderate practice of the three (democrat, lasses-faire, and authoritative) with a dominant use of authoritative leadership style used by school leaders. Furthermore, lack of training, lack of regular support, unavailability of educational resources and principals’ role diversity are among the major factors that hinder school leadership effectiveness. Generally, from the findings of the study, it was concluded that school leaders were not effectively playing their leadership roles as instructional leaders due to limitations of capacity and other resource constraints found in the school. Therefore, it was recommended that Zone Education Offices and the Regional Education Bureau should build the leadership capacities of the school leaders by providing necessary leadership training and technical, material and professional support to secondary schools. School leaders should also be strongly committed to having instructional leadership roles and use more of the combination of the three leadership styles depending on the situation as they are needed than the dominance use of a single leadership style in their school administration