Most school dress code requirements are enforced to maintain a certain culture or appearance of the institution as a whole. Proponents of uniforms, for instance, claim that they unify students and create a sense of "oneness" that can eliminate common problems, such as teasing and bullying children because of what they wear. Dress code requirements are also enforced to discourage violence or sexual behavior in school. If a girl can't show off her bare midriff or a boy can't hide a weapon in his baggy pants, school officials consider this a preemptive measure against what could happen if sex and violence were tolerated in schools.
Most schools that enforce dress code requirements are attempting to eliminate anything that could be offensive or negatively suggestive. This usually includes body piercings, too much bare skin, T-shirts with suggestive language, hats, brightly colored hair, tattoos or short shorts and skirts on girls. Some schools even ban flip-flops or white T-shirts, since they are considered too "casual" or suggest what a student would wear in a nonacademic setting.
Dress code requirements often result in a system of punishments and rewards for students. For example, most schools that have strict dress code requirements will issue detention or some other form of punishment if a dress code rule is broken. Conversely, many schools have "free dress" days or allow certain exceptions on days like Halloween. This can send a message to students that self-expression is only OK when someone else mandates it and that punishment will follow otherwise.
Opponents of school dress code requirements often say that self-expression is directly related to what a child is able to wear. Clothing, therefore, gives the student an outlet for showing his or her personality and thereby reinforcing an identity. Identity formation may be harder to achieve if the student is limited is what he or she is able to wear. As children, and especially as young adults, clothing is often a medium through which we can know ourselves and perceive others.