I doubt that your parents will be impressed with what other teenagers have to say about self studying. I will tell you, and you can share with your parents, what colleges think about it.
When I was going through the admissions process a couple of years ago, I went to an Exploring College Options event, which had reps from Harvard, Stanford, Penn, Duke, and Georgetown, among others. During the Q&A, someone asked, “What do you think of applicants who self-study for additional AP’s over and above the AP classes they take?” One rep responded, “Please don’t do that. We’re not impressed by that.” The other reps all nodded.
You’re a freshman. Get through this year with a 4.0 (or damn close to it) before even thinking of broaching the subject.