Cambodian upper secondary education is divided into two tracks: science and social science. Students make their track selection in grade 10 and begin their enrollment in grade 11. The enrollment in the science track has witnessed a steep decline from 96% in 2014 to 34% in 2020, while the enrollment in the social science track has seen a remarkable surge from 4% in 2014 to 66% in 2020. This tendency poses a significant challenge to the government's endeavors aimed at promoting workforces in science, technology, engineering, and mathematics (STEM) fields. This survey study aimed to examine factors influencing students to leave science-track classes. The survey was administered to 696 grade-12 students from 20 upper secondary schools. The two-level hierarchical linear modeling (HLM) was used for data analysis. The findings revealed that at the individual level, age, ease of national examination, high passing rates, preference for good grades, expense on private tutoring, STEM major choices at the territory level, attitudes toward science, parental advice, and family income significantly influenced students' decision to opt for social science track over science track. At the school level, school location was a significant predictor of track choices. The findings were discussed with practical implications to improve enrollment in the science track at Cambodian upper secondary schools.