J.B.
Hi M. - I am a test prep instructor and have been teaching SAT and ACT prep for 8 years. A good test prep program can help tremendously with all parts of the exam, particularly reading. I have worked with students who are slow and struggling readers but didn't qualify for an extended time accommodation and have been able to teach them strategies that help them move through the passages more quickly and thoroughly.
Group test prep is the most cost effective and a good program can help your son meet his goals. If there isn't a group course in your area that is high quality and fits his schedule, all of the big companies offer on-line classes as well. The company I work for has a very inexpensive large on-line group course (20 students) or slightly more expensive small group on-line tutoring limited to 6 kids. The small groups are great because they can group like students together such as kids who need to focus on reading or math or kids who can do advanced work in one subject area. I think that other companies have similar offerings.
Private tutoring is also a good option but can be expensive. If you can make that investment, ask around for recommendations from people you know. A comprehensive tutoring program typically takes about 20 hours of one-on-one instruction and depending on the rate in your area, can cost anywhere from $50-$100 an hour or more. Expensive, but far and away the most effective option.
I would recommend that he try the SAT and see if he likes that test better or performs better. Both exams are accepted by all schools so it really is a matter of performance and preference. That said, the new SAT is very similar to the ACT now so he might not see a substantial difference.
Finally, while self-study can work well for some students, it is particularly hard for a student who struggles with reading to successfully study from books or even websites (except for on-line classes and tutoring, where the student works in real time with a real person, just via video instead of in person). Also, self-study tends to be a great way to practice what *isn't* working and inadvertently reinforce bad habits and ineffective strategies.
If you'd like more info, feel free to PM me. You can always call any of the large test prep companies (I'll tell you which one I work for via PM, I don't want to "advertise" here) for a free consultation over the phone.
Hope that helps!