Double check your handbook. Not sure our situation will help but maybe it will if you approach the administration -
DD can also wear a plaid or khaki uniform skirt. The guidelines were 1 inch above the knee for years but just officially changed to mid-thigh. It changed because parents voiced that kids grow, bodies vary and tall girls have longer legs. Now, if the girls show that their skirts are not rolled at the waistband, no dress code violation. It's not perfect but maybe you can suggest it as a determining factor. My DD is in 7th at a K-8th school and I don't want to even buy new uniforms at this point so I definitely wouldn't if I were you! Of course DD and friends have figured out a loophole in the system - DD is squeezing into her OLD skirts because they are shorter without the waistband rolled.
Mom to Two Wild and Crazy Boys and One Sweet Baby Girl