I wore a skintight black sheath gown to one I went to in the town I lived in [I went to school somewhere else] Fuck pastel, lace and flounces. Sort of like this, but off one shoulder instead of a halter. This was back in 1979 in western NY state. There was quite a disruption when I walked into a sea of this.
I have no intention of spoiling anything for anyone. Just sharing my lifetime of wisdom with the internet. Things like proms are a big to do about very little, most people don’t enjoy them, yet spend a lot of money and emotional resources on trying to make it a memorable experience. Some people need to hear now and then, “you’re not missing anything” or “you don’t have to do what everyone else thinks is interesting or important.”
I’ve got a bone to pick with your spelling.
Aaaaaaahhhh! For that unforgiveable pun you get 40 lashes with a wet noodle!
You actually make a good point–these days. I think that, currently, formal-wear rentals, florists, limo rentals, etc., are guilty of brazen gouging. And I felt bitter about my social failure in high school (nothing has improved since).
Interesting question: Would a wizard robe meet a requirements of a “dress” (as in The Middle).
You might want to qualify your statements. Many people do enjoy their proms, and many do so without making any major investment. I wore a used vintage dress to mine, went to a nice little local restaurant beforehand, and had a good time dancing and spending time with my friends. Missing prom isn’t the end of the world or anything, but for most people it’s a good time and it’d suck to miss it for no good reason.
For the OP, I’d advise making a stink about it. At the very least, you’ll give some hope to future students facing similar issues.
Formal wear can be a kick - especially for the young with a sense of humor.
Maybe both wear tuxedos - maybe with corsages on the cummerbunds.
I liked aruvqan’s trick - showing up looking like you’re straight out of a James Bond movie while all the “normal” kids are in ill-fitting pastels with aluminum foil and dime-store fabrics for decorations just might make a better statement of you vs. them.
But yeah, hick towns are noted for being run by hicks - be above them.
Unless you can get the ACLU to sue the bastards in your names.
Dance with other people? Socialize?
Are you expected to dance only with you date?
Another idea: I’ve seen two couples come to prom in costumes. One wore civil war period dress and the other were dressed as Leia and Han Solo. Both times it was areal hoot and everybody enjoyed it. Is there anything in hers or her dates interests that might serve?
The point is - try to make this fun. Try to bring your own personality to it without turning it into a grim conflict. For many people it’s the very last chance they get to party as a “kid.”
Do you think I would have the nerve to try that? It’s bad enough I am not sociable and I didn’t like the dance music played (in 1967), but I couldn’t see myself as Reggie approaching some other guy’s Midge. That’s just the way I was.
Some do. Every year or so a judge makes the news for censuring a female attorney who dares to wear pants.
Cite?
Not sure about every year. But here’s one example
There, like in the OP, the problem is not with the woman who is wearing a pantsuit instead of a dress or skirt.
I recall stories that when Australia first dealt with gender anti-discrimination laws in the early 1970s, employers ran ads like, “Laborers - must be capable of carrying 40 kilo loads and be willing to strip to the waist in hot weather.”
Touché! 
Not a clever thing, it’s an obnoxious thing.
Meh, I spent so much time with doctors and in hospital by the time I was 12 I had no body modesty left. I at the age of 18 before I screwed my back over by breaking it could easily have carried [and did carry] 40 k loads, and I would have had no issue stripping to the waist as long as they didn’t mind the number of guys getting punched out for being lewd at me.
Exactly. Capable of carrying 40 kilo (88 lb) loads is a reasonable job requirement. Stripping to the waist, not so much.