Koukou is a Japanese term that refers to high school, specifically the educational institution that students attend after completing junior high school. In Japan, high school typically lasts for three years, and students usually enroll around the age of 15. The curriculum includes a mix of academic subjects, extracurricular activities, and preparation for university entrance exams. Attending koukou is not mandatory in Japan, but most students choose to continue their education. High schools can be categorized into different types, such as general high schools, vocational high schools, and specialized high schools, each catering to various academic and career interests.