This study examined the factors contributing to the differences in academic performance between public and private schools in Republic of Guinea. Public and private schools were randomly selected and used in the study. The participants were students in the last year of elementary, middle and high schools, their teachers, and schools administrators. The data was mainly gathered through survey questionnaires, interviews, check lists, and document analyses. The findings show that students are almost evenly distributed between public and private schools in terms of characteristics and socio-economic status; therefore, the home input factors have yielded little or no significant differences except for the mothers occupations and times spent on school activities at home. The school input factors such as teachers working conditions, school facilities,lack of resources, and directors'' autonomy in decision making are found to be the main significant factors that are contributing to the differences in academic performance between students in the public and private schools studied.