Waffles:
Given son's performance in class (3.9) he's definitely capable. I would have him look at the different areas which made up the aggregate score. Sometimes the "verbal" can be broken down--reading , grammar, etc.(I think College Board Offers this) As Fenway noted timing can be a factor. Practice and familiarity with the type of questions can improve scores--there are practice books, and College Board used to give a "Question of the Day" on their website. I have heard that the ACT ties in more with what is taught in school curriculum. That is an option.
Son's former math teacher gave him a tip which came in handy. When asked if she had any tips on the SAT, she said "Make sure you are answering the questions in the right bubbles (Scantrons)" . Son had originally skipped a question to go back to and his numbers were off by one ..he caught it upon review. It's possible that happened to your son. There's time to turn it around. I am guessing your son is a junior? Good luck!