EEBTTF is SOooo dead-on right. The value of prep courses is primarily in learning the test, not re-learning the areas the test covers. My SA daughter didn't need much help with ACT prep, but my other daughter moved her score 9 pts on the ACT by taking mock exams and then reviewing her answers with a tutor (in person). Be aware that there is huge variability in the quality of tutors out there.
If you live in an area with HSs that are putting athletes into Division 1 football or basketball programs, have your DS contact a head coach or two. DS can tell them about his SA goal and ask them for POCs for reputable scholarship counseling services in your area. Do Not scout for one yourself on the internet (gets real sleazy, real fast). Reputable athletic scholarship counseling services match HS Athletes to schools, which often involves improving given athlete's SAT/ACT scores. A good athletic scholarship counseling service will know EXACTLY who the best test tutors are in your area, We found a counseling service in our area that ran a mock ACT and SAT twice every weekend. The testing itself wasn't expensive; optional one-on-one post-test exam review and tutoring was a little pricey, but it sure worked DD#2! When she took a real scored ACT, she'd dissected 100s of ACT questions, and had 12-14 mock ACT exams under her belt. It was just "another day at the office" for her. She hit her mark and got into the State school she wanted to attend; probably saved me around $100K over sending her to a "Joke School" for a "College Experience."
Whatever his results are, Kudos to your son for taking a shot at getting into an SA. Its "A Road Less Traveled By" and any kid who chooses it and makes the effort to apply is special IMO.
BTW: The are ACT and SAT "Timers" that ARE LEGAL to use during the test. They graphicly display time remaining in a given test period, (one less thing for the DS to worry about). About $35-$50 new amazon; about $25 used (once?) on Ebay
Congrats on the Kid; good luck.
Note: I should add that our USNA DD was a recruited athlete (no LOA). We hired a scholarship counseling service for her because she wasn't exclusively focused on USNA and the service helped us get a handle on the broad/tangled college recruiting process. DD#2 (the one who took advantage of the help with testing) was not a recruited athlete, but she found that coaches were happy to share info to help her, and counseling services were happy to let her test and tutor along with their client athletes