I work part-time for Revolution Prep. RP has a big presence in California and you can probably find a group class or private tutor near you to prepare for the fall round of testing. I chose to work for this company because I really believe that it is the best curriculum, fairly priced (scholarships are available for those who need financial assistance) and they only hire a small % of applicants. I can't speak to the specifics of the other companies, but I can say that I frequently get requests to tutor students who have already done prep work with other companies because their scores did not increase as much as they wanted, and our referral rate is over 90%. So that's my admittedly biased 2 cents! The website is revolutionprep.com.
Good luck with this!
ETA some additional info:
Part of the decision will be knowing how many more points your child is shooting for. A comprehensive test prep program, including 15-20 hours of classroom instruction or private tutoring, an hour of homework per week, 5 full-length practice tests in a mock test environment, and specific feedback for each student (mock test score reports, 1:1 work with a tutor) should yield a 200-300 point improvement, on average. This normally costs about $500 for a group class or close to $2000 for private tutoring. If a program can't tell you what the average score increase is, doesn't offer practice tests in a mock environment, and doesn't include feedback specific to your child, I would question the program's worth. Merely teaching a class from "the big blue book" isn't any more effective than having a child teach him- or herself from "the big blue book" at home, and most students just aren't that effective at teaching themselves.
Also keep in mind that there are some very good on-line courses that can be great for students who like to learn on-line and those can be less expensive than a live class and way less expensive than tutoring.
Finally, consider the cost an investment. Depending on the student, a higher SAT or ACT score can affect scholarship and financial aid potential, making the hundreds (or even thousands) that parents invest in test prep pay for itself many times over. For students who are not candidates for scholarships or financial aid, then you have the benefit of your child knowing that he or she did all that he or she could to land in the school that's the best fit for him or her. It's hard to put a price tag on that, but I would imagine it's worth the investment, particularly if it's a school that can open the door to broader, more lucrative career choices.
Whatever you decide, know that it's well worth the investment. I was a very good - but not elite - test taker in high school. With test prep, I could have earned an elite-level score, which would have gotten me a LOT more scholarship money and I would have borrowed a ton less and not have paid back my loans for 15 years. So keep the big picture in mind as you weigh your options.
