Harmon attended John H. Guyer High School in Denton, Texas. He played alongside his childhood friend Jalen Wilson.[1] As a freshman, he averaged 14.1 points, 4.7 rebounds, 4.6 assists and 1.6 steals per game to help his team to a 30–3 record, a District 6-6A title and the area finals. As a sophomore, he averaged 18.7 points, 4.2 rebounds, 4.8 assists and 1.5 steals per game to help his team to a 25–6 record, a District 6-6A title and the Bi-District finals. As a junior, he averaged 15.7 points, 5.2 assists and 1.7 steals per game. As a senior, he averaged 20.3 points, five assists and 4.4 rebounds per game. Harmon was a three-time Texas District 6A co-MVP during his career.[2] He was selected to play in the Nike Hoop Summit.[3] He committed to playing college basketball for Oklahoma over offers from Baylor, Marquette, Oklahoma State and Texas.[4]
College career
On November 5, 2019, Harmon made his college debut, scoring a freshman season-high 23 points in an 85–67 win over UTSA.[5] As a freshman, he averaged 7.4 points per game.[6] On January 23, 2021, Harmon scored 22 points in a 75–68 upset win over ninth-ranked Kansas.[7] As a sophomore, he averaged 12.9 points, 3.4 rebounds and 2 assists per game, earning All-Big 12 honorable mention.[8] After the season, Harmon transferred to Oregon.[9] As a junior, he averaged 10.8 points, 2.6 rebounds, and 2.1 assists in 31.5 minutes per game. Following the season, he transferred to Texas Tech.[10]