One of the most common proposals put forth for reform of the American system of education is to require school uniforms. Proponents argue that uniforms can make schools safer and also improve school attendance and increase student achievement. Opponents contend that uniforms have not been proven to work and may be an infringement on the freedom of speech of young people. Within an econometric framework, this study examines the effect of school uniforms on student achievement. It tackles methodological challenges through the use of a value-added functional form and the use of multiple data sets. The results do not suggest any significant association between school uniform policies and achievement. Although the results do not definitely support or reject either side of the uniform argument, they do strongly intimate that uniforms are not the solution to all of American education's ills. (Contains 6 tables and 2 notes.)