Concerns about safety in urban schools have led many school districts to require
uniforms for their students. However, we know very little about what impact school uniforms
have had on the educational environment. In this paper we use a unique dataset to assess
how uniform adoption affects student behavior and achievement in a large urban school
district in the southwest. Since each school in the district could decide independently about
whether or not to adopt uniforms, we are able to use variation across schools and over time
to identify the effects of uniforms. Using models that include student and school fixed-effects
along with school-specific linear time trends we find that uniforms generate improvements
in attendance and test scores. These results are particularly strong for girls in middle and
high school. We also find evidence that suggests behavioral problems shift towards less
severe infractions for both genders in middle and high school. Finally, uniforms reduce the
likelihood that girls leave the district for alternative education options, potentially providing
a tool for retaining students in the face of increased school choice options.