Koukou, or high school in Japanese, typically refers to the educational institution for students aged 15 to 18. It is the third level of the Japanese education system, following chugakkou (junior high school). Students in Koukou often prepare for university entrance exams and participate in various extracurricular activities, such as sports and cultural clubs. In Japan, Koukou is not mandatory, but most students choose to attend. The curriculum includes a mix of academic subjects, such as mathematics, science, and literature, along with elective courses. Many students also engage in juku (cram schools) to enhance their studies and improve their chances of entering prestigious universities.