At the 1994 World Junior Championships, Achon became the first Ugandan to win gold, running the 1500m in 3:39.78. Victory was followed by offers of scholarships from a number of US colleges and he chose George Mason University. In 1996 he won the 800m NCAA title, setting a new US college record of 1:44.55. Later in the year, he ran in the heats of the 1500m at the Atlanta Olympics, serving as captain of the Ugandan Olympic team.