The study aims to examine the environmental literacy level of G.C.E A/L students (comparable to British Advanced Level) in the Kandy District, Sri Lanka, and to evaluate environment modules embedded into the curriculum. Furthermore, we find the relationships between environmental literacy level and socioeconomic and discipline levels. A survey with a sample of 300 students was selected randomly from four different disciplines, with 25 students in each subject (biological science, mathematics, arts, and commerce) from three different types of schools (Public, Private, and International). A piloted, self-administered, and structured questionnaire with 44 items under six sections (personal background, environmental issues, attitudes, behavior, suggestion, and mitigation) was randomly distributed among the study sample. Results showed that most respondents reside in an urban area, the education level of parents was positioned in the G.C.E. (A/L) category, and the monthly total family income was more than SLR 90,000.00. Overall, the environmental literacy (EL) was similar among students of three different types of schools. The type of permanent residence, discipline, and educational background of parents were recognized as determining factors of EL levels (p < 0.05). The environmental literacy knowledge of biological science students was the highest (44%), followed by mathematics (36%), art (32%), and commerce (28%). Furthermore, the EL of the biology discipline was significantly different from commerce (18%) and art (14%) students. Students acquired environmental knowledge from television and radio (44%), internet (22%), school (27%), and parents (7%). The A/L Curriculum evaluation results proved that much less environment-related components were included in the commerce, art, and mathematics subjects. Of the disciplines, geography (35%) and biological science (11%) included a higher amount of EL knowledge, comparatively. Students suggested that recycling/ reuse of waste conserves natural resources, the green building concept, and the use of public transportation to conserve the environment. This study recommends that environmental concepts should be integrated with formal G.C.E A/L syllabus with activity learning, especially for non-science disciplines, and that environment-related television and radio programs should be enhanced.