Meh, prom wasn't for me. I didn't have a date, and for sure I knew I wouldn't be allowed to go as female even if I was out to my parents and friends and had clothes at the time (which I didn't.) I invited several friends to a dinner (which you would have had to pay separate from the $75 prom ticket) but only two came, so that was kinda disappointing. One of them didn't even follow the dress code (nice shirt and shorts/pants) and arrived in his trademark university T shirt (always Creighton or Nebraska) and basketball shorts.
Some of the LGB(T) (I put the T in parentheses because not many of the people at any of them know much about transpeople, some are even offensive about it occasionally, saying things like "you're OK the way you are, don't change" or "You're just trying to turn gay guys straight (lol the opposite of what some straight guys think)") caucuses on campus are planning a so called "pride prom," to make up for the many people who were not allowed to go to their prom the way they would have wanted (like not being able to bring a date of the same sex or dress as your preferred gender) so that's pretty cool.
It may be difficult, but if you really want to wear a dress to prom and you're facing opposition, it may be best not to go rather than risk a suspension or other discipline from the school, especially if you were kinda meh on going otherwise. If you really want to go, for sure fight it. Go straight to the superintendent of the district, it may save you time and hassle to do it that way.