Well...it's hard to say what you're doing "wrong" without actually observing you. Just be sure you are doing things by the book. When approaching an intersection, you want to clear left, right, left. You also want to set a point of decision when approaching any intersection with a traffic light. When stopped at a traffic light, be sure to leave atleast one car length of space (space cushion) in front of you, as the light changes, you should be delaying at start up counting 1,2,3 to give the vehicle in front of you time to acclerate while giving you the proper following distance, and simutaneously clearing left, right, left again.
Since your on-road sup is training you and deducting you with "strikes", why dont you ask him what exactly you are wrong, and what you can do to fix the issue. At this point in the game, his opinion is the only one that counts, regardless of whether it is "right or wrong".