If you have someone to help tutor you in areas you're weak in, that can be just as helpful, if not more than an expensive prep course. I was really weak in math so my boyfriend tutored me a couple hours a week for about a month. I bought the Kaplan test prep books on Amazon and that worked just fine for me. I honestly don't think a class would have raised my math score any higher. Got a combined 305 the first time, combined 320 the second time and a 5 on the writing. Studied for about a month beforehand both times. If you're not disciplined enough to structure a study system for yourself, a class may be worth it, if only just to keep you on task.