Football Cunningham attended nearby
Silverado High School in
Las Vegas for his freshman season. His father, who had previously coached his youth teams, was hired as the football team's
offensive coordinator and for the track team's staff in December 2009. In August 2011, his father resigned his positions and transferred his son to Bishop Gorman just prior to his sophomore year. Due to NIAA rules which require a transfer student to wait a year before participating in athletic activities, Randall II was required to sit out his sophomore year in both football and track and field at Bishop Gorman. By his junior year, his
40-yard dash speed was laser-timed at 4.6 seconds. By that time, he had added offers from
Kansas State and
Yale. In the five previous seasons under head coach
Tony Sanchez, Bishop Gorman had gone 60–5 and not lost by more than 14 points. Gorman trailed 14–12 with 8:35 remaining when Cunningham
fumbled. Washington scored a touchdown and then another following Cunningham's third
interception, resulting in a 28–12 defeat. Subsequently, Cunningham led Gorman through an undefeated Southwest League regular season, marking the seventh consecutive such occurrence for the school. By mid-November, Cunningham stated "I like
USC, UCLA, Kansas State,
Texas, ASU, and
Indiana - and
Oregon as well". On December 7, he led Gorman to a 48–14 victory over
Edward C. Reed High School in the state championship, rushing for 4 touchdowns and 213 yards on 22 carries and throwing for a touchdown and 111 yards on 9-of-11 passing. Cunningham was briefly recruited by
Clay Helton, USC quarterback coach under
Steve Sarkisian, but USC did not make him a football scholarship offer. After accepting a track scholarship to USC, Cunningham announced he would attempt to walk-on to the football team. As a freshman, he won the May 20, 2011 NIAA AAAA high jump championship with a jump of . As a sophomore, he sat out of NIAA competition after transferring. On June 24, 2012, Cunningham established the USATF 15–16 age group Outdoor Track & Field record with a jump of . Cunningham won the August 2012 National AAU Junior Olympic Games high jump with a jump of . He actually won the 15–16 age group with a height of . The Junior Olympic age group record of by Johnnie Bartley had stood since 1986, By April 11 of his 2013 junior season, he had already cleared , which was the NIAA state championship record, four times that season. He earned the 2013 Nevada Track & Field
Gatorade Player of the Year award. In the August 2013 AAU Junior Olympics, he was second or third in the 17–18 age group with a height of or , depending on the source. On January 3, 2014, he made a verbal commitment to the
USC Trojans track team, shunning over 30 football scholarship offers. In 2014 at the annual Mt. SAC (
Mt. San Antonio College) Relays, he set the American high school season best for boys of on the same April 12 day his sister
Vashti did so for girls with . He was surpassed by Bryant O'Georgia of Arizona by one quarter inch in May. Cunningham placed first in the May 24, 2014 NIAA state championship with a high jump of and second with a long jump of . As a freshman at the
University of Southern California, Cunningham finished second at the
Pac-12 Outdoor Championships with a height of and tied for 8th at the
2015 NCAA Division I Outdoor Track and Field Championships (). Two weeks later, he won the U.S. Junior National Championship with a . His top 8 finish in the NCAAs earned him All-American recognition. In his freshman year, Randall was coached by 2-time Olympian
Jamie Nieto who took over as the USC assistant coach in charge of jumps and multi-events on August 20, 2014. Later that summer he earned a gold medal at the
2015 Pan American Junior Athletics Championships with a jump of . His sister Vashti also won gold at that same competition. As a sophomore, he was second again at the Pac-12 Outdoor Championship with a height of and won the
2016 NCAA Division I Outdoor Track and Field Championships with a height of , which is an outdoor personal best. Cunningham no-heighted at the July 8,
2016 Olympic Trials qualifying round after three unsuccessful attempts at . The trials were held during a torrential downpour that was deemed severe enough to suspend the women's pole vault event and that seemed to impair the men's discus event. As a junior, Cunningham was recognized on March 6 as the west region Men's Field Athlete of the Year for the indoor season by the United States Track & Field and Cross Country Coaches Association. He placed fourth at the March 11,
2017 NCAA Division I Indoor Track and Field Championships with a height of , earning him another All-American recognition. As a senior, Cunningham won the
2018 NCAA Division I Indoor Track and Field Championships with a USC record height of . ==Personal life==