About half of schools around the country have dress codes policies. A dress code identifies what clothes cannot be worn to school. A school uniform policy defines what clothes must be worn to school. Dress codes limit clothing options while school uniforms define clothing options.
I believe school uniforms may be part of a broad array of programs and approaches that a school may adopt to bring change. However, as a standalone measure, it implies that schools are simply trying to find an easy fix for difficult and complex problems.