Thomas Harper was born and raised in Knoxville, Tennessee where he played his prep ball for Karns High School. Harper was a standout on both sides of the ball, and despite playing on defense in college, he was a record-breaking receiver for his varsity squad.
As a junior in 2017, Harper became the first player in Karns history to go over 1,000 receiving yards in a season. He totaled 1,086 yards and 11 touchdowns en route to being named a First-Team All-State selection. As a senior, he pushed his numbers even further by resetting the record book with 1,279 yards and a whopping 18 touchdowns.