I go to a public high school and there are about 560 people in my grade, I’m ranked like in the top 3 percent of my class. I have a 4.25 weighted GPA, 3.8 unweighted. I got one B during my junior year, in a regular physics class (embarrassing, i know) but my teacher hated me lol. 
I took 2 APs and got As in both, and precalc honors and I got an A. I got a 5 on the APUSH exam (idk if this matters to them) and so far on practice sat tests I’m scoring in the 1930ish range. But I’m working on improve my score at least to 2000 by the October test. I’m also president of a JSA club at my school and EIC of the newspaper, and play on the lacrosse team. I am now a senior taking AP Econ, american democ honors, ap calc, and ap english
To be competitive for USC, you should aim for a 2100. A 2000-2100 would be a low reach but I wouldn’t apply if your under a 2000. It would be a stretch. However, don’t let that totally discourage you. Essay are very important.