Johnson was became a top-5 wideout in the entire country while prepping at Warren Easton High School in New Orleans. As a junior, Johnson caught 87 passes for 1,433 yards and 17 touchdowns. As a senior, he hauled in a whopping 94 passes for 1,589 yards and another 17 scores. After being named a First-Team All-State selection and a member of the 2014 All-USA Team by USA Today, Johnson earned a five-star rating by Rivals and was considered the No. 2 wide receiver prospect in the entire country. After receiving an invite and participating in the Under Armour All-American Game, Johnson accepted an offer to play for the LSU Tigers.