I have had 3 admitted to USC and always sent the mid year because it is stated in several places to do so:
FROM THE USC COMMON APP:
Recommendations Required:
School Report
Counselor Recommendation
Mid Year Report
Final Report
1 Teacher Evaluation(s)
0 Other Evaluation(s)
Writing Supplement Required:
Not Required
Personal Essay Required:
Required
From the USC Admission FAQs:
How do the grades I earn during my senior year of high school factor into USC’s admission decision?
Generally, for the purposes of admission into USC, we review an applicant’s coursework from grade 9 through the first term of his or her senior year. Students need to use the Mid-Year Report Form included in the Common Application or visit www.usc.edu/midyeargrades to submit their fall grades as soon as they become available.
Once admitted, all students are required to submit an official copy of their high school transcripts to verify their graduation dates. Students’ transcripts will also be reviewed to ensure that they have maintained a continued level of academic achievement. A serious downturn in a student’s senior year could result in the rescinding of an admission offer.
The USC checklist:
http://admission.usc.edu/firstyear/prospective/checklist.html
Ya, I would be sure mid year grades are in.