A school uniform is a uniform worn by students primarily for a school or otherwise educational institution. They are common in primary and secondary schools in various countries. Although often used interchangeably, there is an important distinction between dress codes and school uniforms: according to scholars such as Nathan Joseph, clothing can only be considered a uniform when it "(a) serves as a group emblem, (b) certifies an institution's legitimacy by revealing individual’s relative positions and (c) suppresses individuality." An example of a uniform would be requiring white button-downs and ties for boys and pleated skirts for girls, with both wearing blazers. A uniform can even be as simple as requiring collared shirts, or restricting colour choices and limiting items students are