You better put down that math homework, this is something you want to hear. First of all, try to give Dad a break next time you ask him for help on algebra. Trust him when he walks you through the steps; that guy knows what he's talking about. It might also be a good idea to start the homework before 10pm. You're not a night owl, and you never will be (but that's okay, love!).
Keep working hard in school, but know that each class, each assignment, each test will always turn out okay. Remember the important things. Remember that in the grand picture, that one moment is so small. Don't take chemistry. You'll hate it and you'll never need it.
Do us a favor, and pay attention to Jess every so often? I'm dying for memories of him before the age of 16, and I know he sometimes pretends to cheat off your paper, but don't worry about it. Boys are immature and they get better.
Make sure you also catalog a few mental voice recordings of Cady's cute speech impediments, because all of a sudden they'll be gone and everyone will forget. Be nice to Leah and don't freak out when she borrows your clothes--you know you borrow hers too without asking. On second thought, just be sweet to everyone. And probably don't pull the feather-and-shaving-cream trick on poor little Levi. Everyone will laugh about it later, but you'll just feel guilty.
Don't pick up that copy of Seventeen in the library, and you'll avoid years of self-confidence issues. Go for the Family Circle and become an expert decorator or something instead.
Keep on spending all your free moments with the family; you'll never regret that. Be excited about growing up. Don't be scared every time a cute boy looks your way. Kiss Porter's cheeks. Go ahead and want 12 kids someday. Do what you do and be happy.