Reducing dropout rates is a major issue in Cambodia. This study examined the effects of school-level and student-level factors on dropout in rural Cambodian primary schools. We collected data of the same students over 3 years by visiting the same school. We used questionnaires for students and parents, checklists of school facilities, checklists of teacher characteristics and Khmer language and mathematics tests achievement as research tools. We found that the effect size of the school was small: students who dropped out had similar characteristics -- even when dropout rates varied among schools. At the school level, teacher absence in both cohorts, mean interaction with teachers in higher-grade cohorts, and mean test achievement in lower-grade cohorts were significantly associated with dropout. At the student level, age at first school entry in both cohorts were significantly associated with dropout. In cohort 1, gender, relative achievement in class, parental educational attainment, economic status, parents' educational aspiration, and school distance were related to dropout. In cohort 2, repetition experience, absence, educational aspiration, teacher interaction, living with parents, and time spent helping the family were related to dropout. Reducing teacher absence and late school entry were key factors of preventing from dropping out of school.