Johnson grew up in Sun Prairie, Wisconsin and initially attended Sun Prairie High School.[1] He transferred to Nicolet High School after his freshman year.[2] As a junior, Johnson averaged 19.5 points, 8.7 rebounds, 5.0 assists and 3.1 steals per game.[3] He averaged 26.7 points, 10.4 rebounds, 4.1 assists, and 2.4 steals per game during his senior season.[4][5] Johnson committed to play college basketball at USC over offers from Colorado State, California, Elon, and Kansas State.[6]
College career
Johnson played in 27 games during his freshman season with the USC Trojans, averaging 1.2 points and one rebound per game.[7] He became a starter as a sophomore and averaged 9.2 points and 5.0 rebounds per game while also being named to the Pac-12 Conference All-Defensive team.[8] Johnson repeated as a Pac-12 All-Defensive team selection as a junior while averaging 10.9 points, 4.6 rebounds, 3.3 assists, and 2.2 steals per game.[9] After the season, he entered the NCAA transfer portal.[10]