Waller earned two varsity letters under head coach Tyree Spinner at the Avalon School in Washington, D.C., after spending his first two seasons at Archbishop Carroll. In his first two seasons, Waller threw for more than 2,600 yards and 24 touchdowns as a quarterback before moving to defensive back at the Avalon School. He tallied six interceptions as a junior and was on The Washington Post’s All-Met preseason watch list in 2017.