Testmasters or Powerscore..or other?

<p>Would anyone recommend any specific SAT Test Prep which has worked for them- other then self-study. My brother needs the prep and even though he has a 2100(first attempt) he is sort of a slacker and needs some sort of course to keep him on track. I was considering Testmasters or Knewton, any one else with other advice?</p>