Hey Jaimee;
WOW!! I was particularly interested in checking this out, as I am a parent (though my girls are only 3 and 1.5) and a teacher. My specialty is music, but I spend most of my time teaching grade 5, so most of the students I contact are really only two or three years younger.
Coming from that point of view, I'm always ecstatic when I see young people pursuing musical interests, particularly when they have an obvious level of talent. FWIW, I STARTED playing when I was twelve, and didn't start singing until years later. Your performance was wonderful - and I say that to mean "not just for a twelve-year-old." Wonderful for any age!
Don't quit school.... there's time to develop your musical interests along side, within and around school. Certainly don't give up on the music. It seems clear to me that, no matter what happens, music will probably be (and indeed should be) a part of you throughout your life. I consider myself lucky to be able to say that as an adult. Don't lose it - not that you will.
Your dad is obviously very supportive. You can't measure how important it is to have yourself surrounded by people who support you in your musical pursuits.
Do music because you enjoy it. If you're lucky enough to have it develop into a career, then that's gravy. Don't do music because you feel you have to. It will take the fun out of it.
I also find it refreshing for someone your age to have a wider range of taste in music that goes beyond Eminem and Enrique Igleseas. As you continue your pursuit in music, this open-mindedness that you seem to have will only help you.
Keep it up, and post some more!
Notice, I had no advice on the performance??!! Oh, well...
Chris