The schools will be able to see all of your scores (from the past 3 years I think). Some will take an average of them, some will factor in all scores individually and some will take the most recent. Best thing is to talk to the schools that you are interested in about how they look at multiple scores. The truth is that as long as you don't re-take too many times, and your scores increase when you do retake it I don't really see any harm. If your scores decrease, that is a problem, so only retake if you are fairly confident can better your score (and not waste the money also).