Hello. I have cumulative 3.9 weighted GPA, cumulative 3.7 unweighted GPA, and 4.12 GPA for sophomore and junior years.
And my SAT scores are in mid 1800s with the superscore. I also filled out 7 activities out of 10 in common app.
I’m planning to take one more SAT test on December. Do you guys think i can get into USC or NYU with my school grades and test scores? I’m also aiming for the UCs (except UCB),
Hun the only person who can know that is the admissions counselor. If you want to apply to those schools, then just give it your best shot and don’t base your decisions on what other random high schoolers on the Internet think. James the high school junior and his overbearing mother from Wyoming do not have the qualifications to determine if you are a “high match” or have “37 percent chance by standards of the class of 2013.” Maybe you will get in to those schools, maybe you won’t. Just try, and good luck!
^^ While this is true to a certain extent, there are definitely statistics that can be very useful in predicting whether a school is a match or reach for you. If you google “school name common data set” you can see how you stack up against past applicants.
Here’s the link for NYU:
https://www.nyu.edu/ir/pdf/cds/CDS_2011-2012%20Final_NYU.pdf
With your superscored SAT, you are still below the 25th percentile SAT scores for NYU.
Here’s the link for USC:
http://www.collegedata.com/cs/data/college/college_pg01_tmpl.jhtml?schoolId=1138
With your superscored SAT, you are still below the 25th percentile SAT scores for USC.
Your GPA is good but not great, and you were pretty vague on your ECs. Based on the information you provided in your post, I would say that both USC and NYU are going to be high reaches for you. By all means still apply to both, but make sure that you also have some matches and safeties on your list. Good luck with everything! 
Move this to chance page.