If the kid's halfway intelligent, he should be able to bullshit his way into the prom with the girl. She looks like she could pass for high school age (maybe). Were it me, I'd announce that due to the misguided an puritanical school administrators, I'm aborting my plan. I'd find a brunette girl in a neighboring school district sympathetic to my cause to agree to be my date and get Principal Butthead's approval. Probably all they'll do is check to make sure said proxy exists, and maybe have her year book photo faxed over. Show up with porn chick. At most you might have to pop $30 for a fake ID, assuming your ally wouldn't loan out hers for a day.
Getting a porn chick to go to the prom with you is a pretty cool move. Sneaking her into a prom that she's forbidden from attending, after she's become a national news story is the stuff of legends.