Johnson played basketball for four years at East Technical High School in Cleveland, Ohio.

As a freshman, he scored 27 points and made a game-winning jump shot with 3.1 seconds left against Lake High School to help his team reach its first state semifinal since 1972.

[2] In his junior season, Johnson averaged 31.6 points, 7.4 rebounds and 3.5 steals per game, leading East Tech to its third straight league title and a district semifinal appearance.

[11] He injured his ankle in practice and missed the first game of his senior season, an overtime loss to Georgia Tech.

[15] Johnson scored a career-high 28 points and made a halfcourt shot in a 88–66 upset of sixth-ranked Duke on February 19, 2020.

[18] On August 6, 2020, Johnson signed a two-year contract with Beşiktaş of the Turkish Basketball Super League (BSL).