My Geometry class was where we learned proofs. But I was at a private school and that was 30 years ago, not a public school in CA right now.
I also did Calculus in 10th grade, but I was only one of two kids to do so in my grade (out of 105 in my class). We also had a guy who did Calculus in 9th grade, but his dad was a math professor at the local university. I figured he had an edge