Johnson attended Christian Life Center Academy in Humble, Texas under coach Carlos Wilson.
He averaged 15.2 points, 4.4 rebounds and 1.3 assists per game, while shooting 47.3% from the field, 47.8% from three-point range, and 75.9% from the free throw line.
[3] On November 1, 2014, Johnson was selected by the Santa Cruz Warriors with the 13th overall pick in the 2014 NBA Development League Draft.
[7][8] On November 14, he made his debut for Raptors 905 in an 83–80 loss to the Fort Wayne Mad Ants, recording 12 points, one rebound and one steal in 20 minutes.
[10] The next day, he made his debut for Texas in a 127–117 loss to the Los Angeles D-Fenders, recording nine points, three rebounds and an assist in seven minutes off the bench.
[14] The next day, he made his debut for Grand Rapids in a 107–106 loss to the Sioux Falls Skyforce, recording 11 points, three rebounds and one steal in 24 minutes.