Kingsbury played high school football at New Braunfels High School, where his father, Tim, was head coach. Kingsbury also was a member of the baseball, basketball, and track teams. As a quarterback at New Braunfels, Kingsbury threw for 3,009 yards and 34 touchdowns while leading the team to the Class 5A Division II semifinals and a 13–2 record. He was named the offensive MVP in the Texas High School Coaches All-Star Game. Kingsbury graduated 3rd in his class of 450, and was an Academic All-State selection. In May 2018, Kingsbury was formally inducted into the Texas High School Football Hall of Fame.