At age 13, Lewis began competing in the long jump, and he emerged as a promising athlete while coached by Andy Dudek and Paul Minore at Willingboro High School in his hometown of Willingboro Township, New Jersey. He achieved the ranking of fourth on the all-time World Junior list of long jumpers. Many colleges tried to recruit Lewis, and he chose to enroll at the University of Houston where Tom Tellez was coach. Tellez would thereafter remain Lewis's coach for his entire career. Days after graduating from high school in 1979, Lewis broke the high school long jump record with a leap of . By the end of 1979, Lewis was ranked fifth in the world for the long jump, according to "Track and Field News". An old knee injury had flared up again at the end of the high school year, and this might have had consequences on his fitness. Lewis worked with Tellez and adapted his technique so that he was able to jump without pain, and he went on to win the 1980 National Collegiate Athletic Association (NCAA) title with a wind-assisted jump of . Though his focus was on the long jump, he was now starting to emerge as a talent in the sprints. Comparisons were beginning to be made with Jesse Owens, who dominated sprint and long jump events in the 1930s. Lewis qualified for the American team for the 1980 Olympics in the long jump and as a member of the 4 × 100 m relay team. The Olympic boycott precluded Lewis from competing in Moscow; he instead participated in the Liberty Bell Classic in July 1980, which was an alternate meet for boycotting nations. He jumped for a bronze medal, and the American 4 × 100 m relay team won gold with a time of 38.61 s. He received one of 461 Congressional Gold Medals created especially for the athletes precluded from competing in the 1980 Olympics. At year's end, he was ranked sixth in the world in the long jump and seventh in the 100 m. At the start of 1981, Lewis's best legal long jump was his high school record from 1979. On June 20, Lewis improved his personal best by almost half a meter by leaping at the TAC Championships while still a teenager. While marks set at the thinner air of high altitude are eligible for world records, Lewis was determined to set his records at sea level. In response to a question about his skipping a 1982 long jump competition at altitude, he said, "I want the record and I plan to get it, but not at altitude.