During Carter's junior year in high school he was teammates with Joe Cohen and Reggie Nelson on the football varsity, while in track ran 10.38 seconds in the 100 m sprint, 20.69 seconds in the 200 m sprint and 45.88 seconds in the 400 meters, the best in the United States in that event for 2003. As a senior Carter ran 10.29 s the 100 m sprint, 20.49 s in the 200 m sprint, and 45.44 s in the 400 m. He also set the national high school record in the indoor 200 m, with a time of 20.69 s, thus becoming the first United States high school athlete to run under 21 seconds in that event. At the 2005 NCAA Men's Outdoor Track and Field Championship he finished second in the 200 m finals with a time of 20.08 s.