he major purpose of this study was to examine whether there is difference in academic achievement at grade 9 between students taught in Afan Oromo and those taught in English in grades 7 and 8.Parents and students attitude towards the use of Afan Oromo or English as MO! in grades 7 and 8; and their effect on students' academic achievement was also investigated The study was a comparative study, involving quantitative approach.250 students (145 male and J 05 female) and the. same number of their respective parents were selected randomly following different techniques and participated in the study. Data was collected through· questionnaire, document analysis and interview from, students and their parents. A five point likert scale was developed based on experiences, literature reviews and current practice. It was piloted and its final reliability established as a Cronobach alpha coefficients of 0. 6976. The quantitative data obtained from record offices and from the questionnaire was analyzed using the statistical packages for social sciences (SPSS) version 10. 0. The primarily statistical analyses utilized were descriptive statistics, one sample and independent t-tests, Pearson correlations and one-way ANOVA. Results of the study indicated that there is significant difference in academic achievement between students taught in Afan Oromo and English in grade 9. Students who study f hrough the mother tongue in grades 7 and 8 outperform or achieve more both at grades 8 and 9 than those students who study through the English medium. The result s,'zows that students taught by Afan Oromo and their respective parents have a strong positive attitude towards the use of MT as MO! in grades 7 and 8.Similarly, students, taught in English in grades 7 and 8 and their -parents show_ed negative attitude towards the use of English as medium of instruction, favoring MT medium which is inconsistent with the interview result that indicate negative attitude towards negative attitudes of students and parents to strengthen the advantages mothe.r tongue impose on academic achievements of students . Vlll