As a youngster, Ridley played Pop Warner football in the same league as Baltimore Ravens quarterback Lamar Jackson, Ravens wide receiver Marquise Brown and Oakland Raiders cornerback Trayvon Mullen, in the Pompano Beach area of Florida just 4 miles from the high school he would attend. Ridley attended Monarch High School in Coconut Creek, Florida, where he played high school football for the Knights. He played only three games in his senior year due to Florida age restriction rules, which doesn't allow anyone over the age of 19 and nine months to be eligible. Ridley was rated as a five-star recruit and was considered the best receiver in the class of 2015 according to 247Sports, Rivals, and ESPN. He committed to the University of Alabama to play college football on April 19, 2014.