This study aims to investigate Kazakhstani high school students' environmental knowledge, attitude toward the environment, environmental awareness, and environmental concern, and to present the effect of various extracurricular activities on high school students' knowledge, attitude, awareness, and concern. We surveyed 124 students at various grade levels. Results indicated that Kazakhstani students did not have a strong environmental knowledge base and their awareness of environmental issues is not strong at all, but they had a strong positive environmental attitude. There was no significant relationship between knowledge, attitude, and awareness based on grades in biology, chemistry, physics, math, and geography. Gender did not influence students' environmental knowledge, attitudes, and awareness but year in school did for environmental knowledge. Kazakhstani students were most concerned about air pollution, pollution of rivers and seas, and flooding, and they were the least concerned with overpopulation, radioactive waste, extinction of species, and climate change. Extracurricular activities did prove useful with increasing students' knowledge and awareness about environmental challenges but did not impact their environmental attitude. Our results imply that what is being taught about the environment in Kazakhstani schools is not substantial enough. Educators may modify the curriculum to better address environmental issues in the classroom and add more content and activities.