Thompson was a three-star athlete from England High School in England, Ark., in the class of 2017. He was the No. 797 recruit according to the 247Sports Composite board and No. 769 for On3.com. Thompson was an unranked three-star recruit for ESPN with a 78 grade out of 100. He committed to Baylor over Florida State, Louisiana Tech, Purdue, Texas, and Washington State. Thompson was a two-way player who primarily lined up at tight end and defensive end in high school. He also played cornerback as a freshman. As a high school senior, he guided England High School to a 14-1 record and the 2016 2A state semifinals. He finished the season with 37 receptions for 601 yards and ten touchdowns on offense and 29 tackles, 16.5 tackles for loss, 7.5 sacks, two interceptions, two passes defended a forced fumble, and a touchdown on defense. Thompson led England High School to a 13-2 mark and the 2015 2A semifinals as a high school junior. He finished that season with 52 receptions for 830 yards and 11 touchdowns. On defense, he tallied 91 tackles, 13 sacks, and returned an interception for a touchdown. Thompson also participated in basketball, baseball, and track and field in high school. He originally committed to Washington State before de-committing and switching to Baylor. Thompson transferred from Baylor after the 2018 season. His brother (Blake Mack) played tight end at Arkansas State from 2014 through 2017. Thompson earned First-Team All-Southland Conference honors in 2020 and was the conference’s 2020 Newcomer of the Year.