My dad favors my brother over me?! Please answer...?

I have three older brothers, and I'm the only girl. My two oldest brothers are already grown and out of the house. My third brother and I are only 17 months apart. I'm 16. My brother just recently got his drivers license, and I had asked my dad if I could get mine too. Before (while my brother was still in driving school), my dad told me "Just wait. We have a lot to pay for with this (300 dollars for driving school). Once your brother passes all his tests and gets his license, we'll sign you up for driving school". So meanwhile, I worked super hard in school to make all A's and B's, so that my parents would know I was responsible enough for my license. Now that school is out for summer, and my brother has his license, I asked my dad if I could go to driving school again. His response was "No. Not right now. Your brother needs insurance, and he is going to need a car also. We'll have to do yours another time". My brother failed half of his classes, and he passes the other ones with D's. I'm so angry. My dad was just thrilled that my brother passes his classes. AND not to mention, it was "I" who did most of his work for him! (Cheating, I know. But my brother is able to twist people into doing what he wants them to do). Please help me!? Also, when my brother got his drivers license, my dad came home with a HUGE bag of junk food with everything my brother loves and said "Congratulations on getting your license!".... Should he have been rewarded for THAT?! My brother didn't even share his junk food. He ate it in front of me. What should I do? I really wanted to go to driving school this summer... :'(