School uniforms in the United States
Students in Houston, Texas public high schools are wearing school uniforms. Most public schools in the United States do not require uniforms, though many have dress codes regulating student attire. Dress codes usually include limits on skirt length and skin exposure. They generally include prohibitions on clothing with tears or holes, exposure of undergarments, and anything that is obscene, gang-related, or unsafe. Some school dress codes specify the types of tops (e.g. collared) and bottoms (e.g. khaki) that are allowed, as well as specific colors (often the school colors). In recent years there has been a significant increase in school uniforms (see below) for all levels of schooling. In most cases, while school uniforms vary greatly, a general idea of what is typically permitted includes:
Collared shirts (types vary significantly)
According to the National Association of Elementary School Principals (NAESP), the fraction of American public schools requiring school uniforms rose from three percent in 1997 to one in five (21%) in 2000. School uniforms are fairly common for private schools in the United States, especially for Catholic schools. Although many private school uniforms are similar to the ones described below for public schools, a few still require more formal British-style school uniforms, such as blazers and ties. Culottes are also sometimes substituted for a skirt, especially at Episcopalian or non-parochial private schools. In 1994, the Long Beach Unified School District, in Southern California, required school uniforms in all elementary and middle schools. This began a trend for uniforms in American elementary public schools, especially in urban school districts. President Clinton mentioned LBUSD's efforts in his 1996 State of the Union Address. The adoption of school or district-wide uniform policies (or, alternatively, "standardized dress codes" – which are not as rigid as school uniform requirements, but allow some leeway within set parameters) has been motivated by a need to counter "gang clothing" (or, in the alternative, the pressure for families to purchase upscale-label clothing to avoid their children being ignored by "fashion cliques"), as well as to improve morale and school discipline.
Adolfo Santos, a political science professor at the University of Houston–Downtown, stated that many Hispanic communities in the United States choose uniforms because many immigrants originate from countries with schools requiring uniforms .
In Puerto Rico, the Puerto Rico Department of Education requires all students to wear school uniforms, and only allows for medical exemptions.  Also, almost all private schools also require their students to wear school uniforms.