Not all speech is protected in a school setting. For example, students who wear clothing that follows the latest fashion trend – such as oversized shirts and slouchy jeans for boys, or short skirts and mid-drift cut-out shirts on girls – or clothing that supports a particular sports team, religion, or political point of view, may be prohibited in dress code policies if the student’s choice in clothing draws attention away from the school’s learning environment.
Therefore, limits on dress codes have including the following:
Limits on ‘gang-related’ clothing, sometimes described as over-sized clothing and other clothing meant to show affiliation with a certain gang or group, such as certain colors, logos, brand names, or arrangement
Ban on suggestively-themed T-shirts, such as Marilyn Manson t-shirts
Requirement to wear school colors only
Limits on skirt, shirt, and pant length
Ban on clothing that depicts lewd, sexually explicit, or idecent drug use
Seasonal closthing restriction, such as limits on midriffs and lower backs not being exposed in hot weather
"Baggy pants" restriction prohibiting students from wearing clothin that exposes underwear or body parts in a way that is indecent or vulgar
- See more at: http://education.findlaw.com/student-rights/school-dress-codes.html#.dpuf