Jack Duncan started teaching and coaching at Gar-Field High School in 1966. He was an assistant varsity football line coach from 1967-70. The 1967 football team was undefeated and yielded only 12 points all season. Duncan was an assistant varsity track coach from 1966-69 and head wrestling coach from 1966-80. 

Duncan led his wrestling teams to 10 district championships, four regional titles and one Virginia state team championship. He coached 58 district champions, 26 regional champions and eight state champions. Gar-Field also hosted many district, regional and state tournaments.

In addition to bringing in and developing many great assistance coaches, he also inspired the Gar-Field student body, cheerleaders, Indianettes, choral members, band members, teachers and staff to be invested in the wrestling program.

​Coach Duncan taught you to fight when you think there is no more fight left within you, and how to get up after you've fallen. You learned about sacrifice and how to endure and overcome.

He was well respected throughout the sport of wrestling as evidenced by the many awards and honors he received.