School uniforms, which are called "seifuku" in Japanese, are common in public and private schools in Japan. In the majority of middle and high schools, it is required for students to wear school uniforms, which consist of military style uniform called "gakuran" for boys and sailor outfit as the standard uniform for girls.
Gakuran, normally black or navy, were based on military outfits from the Meiji era, which were inspired by European naval uniforms. The buttons are usually designed with the school emblem as a symbol of respect to the school. Sailor outfit called "sera-fuku" were inspired by the British Royal Navy and usually includes a white blouse, pleated skirt, and a ribbon; there is a summer version and a winter version. A school uniform ranges from about 50,000yen to 80,000yen.
School uniforms are extremely popular especially among girls. It is common to wear school uniforms outside of school as a fashion. Even girls who attend schools where school uniform is not compulsory purchase and wear school uniforms as a fashion trend known as "Nanchatte seifuku" (just kidding uniform). Conomi located in Harajuku is a popular store right now where you can purchase various styles of school uniforms. Girls enjoy customizing their uniforms by selecting different colors and prints.
If you want to try out a school uniform just for fun, you can even rent a school uniform for free when taking purikura (depends on the game arcade)! :)