He should give the SAT another shot. He can still register for the Dec 3 test. EBRW scores can improve materially from 10th grade to 12th grade even without tutoring/practice. The 1450 combined and 690 EBRW would put him below the 25th percentile for Brown.chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://oir.brown.edu/sites/default/files/2020-04/CDS_2021_2022.pdf The composite would be right at the 25th percentile for Amherst and the 690 would be below as well. If retaking the SAT is not an option, then apply Test Optional. The existing score is good enough to submit to USC. chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://oir.usc.edu/wp-content/uploads/2022/06/CDS_2021-2022_FINAL.pdf
Also Google the other schools “CDS” (common data set) to get an idea of the SAT score ranges for each. Wash U, Tufts, Pomona and Claremont will be high and barring a retake, your son might be better off applying Test Optional if offered by those schools.