His parents run the training facility Next Play 360° in Marietta, where they moved from Hempstead, New York, shortly before Henderson's birth.

[1][5] In February 2020, during his sophomore season, Henderson scored a then career-high 49 points and made the game-winning shot in a 92–91 overtime win over Miller Grove High School in the first round of the Class 5A state tournament.

[10] Henderson led Kell to the Class 6A state title game, scoring 29 points in a loss to a Wheeler High School team featuring future top prospect Isaiah Collier.

[11] He averaged 32 points, seven rebounds, and six assists per game in the season,[12][13] earning Class 6A Player of the Year and first-team 6A All-State honors from The Atlanta Journal-Constitution.

[20] On May 21, 2021, he announced that he would reclassify to the 2021 class and join the NBA G League Ignite, declining offers from Auburn and Georgia.

[23] In his second game, on November 26, Henderson recorded a career-high 31 points, six rebounds and five assists in a 112–110 loss to the Santa Cruz Warriors.

[27] In October 2022, Henderson represented the Ignite in a pair of exhibition games against Victor Wembanyama, the projected first overall pick, and Metropolitans 92.

[30] On November 12, Henderson posted 18 points, a career-high 16 assists and six rebounds in a 125–115 victory over the Santa Cruz Warriors.

[38] He made his 2023 NBA Summer League debut on July 7 against the Houston Rockets with 15 points, five rebounds, and six assists.

[39][40] On October 10, Henderson made his preseason debut, putting up seven points, one rebound, and six assists in a 106–66 victory over the New Zealand Breakers.

[42] On October 25, Henderson made his NBA regular-season debut, putting up 11 points and four assists in a 123–111 loss to the Los Angeles Clippers.