Some of the most common reasons given for why there should not be dress codes in schools include the following:

• Students need (especially as they get older) to be able to be individuals.  They should not be forced to comply with someone else's vision of how they should dress.  If they do not get the chance to experiment while they are in school, they will not be as ready to be responsible adults who make good decisions on their own.
• It is too expensive.  If students have uniforms, they will not be able to or will not want to wear those uniforms when they are away from school.  That means that parents will have to buy clothes just to be worn to school -- an unnecessary expense.