If you're cutting here and there without crucially affecting your grade point average then tell your parents why you feel you deserve a break now and then. Just be careful not to make it a habit. I've talked to some of my friends about this and they all agree - we just don't know how to tell our girlfriends about it. I definitely agree with you. A woman is just as capable of paying.
Prom is very expensive.
When I went last year I even volunteered to pay for the pictures. Approach the issue with sensitivity and tact. Most likely, your dates will see eye to eye on this. It's really very unfair to all the other students and always so obvious. I think that teachers should treat all students the same.