The study compares the achievement gap of government and private primary school students in Bangla, English and Mathematics in Bangladesh. The research design used was quantitative, descriptive and comparative cross sectional. The study was targeted at the students of 5th grade of 20 government and 20 private primary schools of Savar Upazila in Dhaka city. Purposive sampling was used to collect data from the 400 students, namely 200 government and 200 private school students. Demographic, socioeconomic and educational data were collected by using a structured questionnaire, and learning achievement test, 60 marks was given for each subject, Bangla, English and Mathematics, 20 marks each. Data were analyzed by frequencies, percentages and mean scores. The results revealed that the mean scores of the private school students were higher than those of the government school students in all three subjects. The mean scores of governments and private school students were 13, 10, and 11 in Bangla, English and Mathematics respectively, while their private school's mean scores were 16, 15, and 17 in Bangla, English, and Mathematics. There was an overall mean achievement score of 34 (56.67%) on government school students and 48 (80%) on private school students. The results show that there is a significant difference between the descriptions of the achievement levels of the two school types. Contextual explanations can be considered, because of the differences in educational qualifications of the parents and the access to private tutoring. The study suggests improving the quality of teaching, the learning materials, remedial support and home-learning activities, especially in English and Mathematics.