Honestly yes and no. I would strongly advise my son not to wear a dress or a skirt in school because I know how a school environment can be. Anyone straying from the accepted norm, be that wearing "opposite gendered" clothing, fitting into the goth / scene / emo stereotype, or what have you is immediately a target for bullying, be it physically or mentally. However, were he to insist that it was what he was comfortable in, I would let him without hesitation.