Jack attended Manhasset High School from 1959 to 1963, where he played two years of varsity lacrosse. His team won the Long Island Championship in 1963, the same year in which he won first team All-Long Island honors. Jack moved on to the University of Maryland, where he played three years of varsity lacrosse. Each year he played, Maryland won the ACC Championship (1965 to 1967). He was a Division I first team All-American in 1966 and 1967, and a third teamer in 1965. He captained the South in the 1967 North/South game and won the Jack Turnbull Memorial Trophy and the Talbot T. Spear Award in the same year. In 1966, he was the University of Maryland's "Junior Athlete of the Year" and won the Powell Lacrosse Award for "Service and Advancement of Lacrosse at the University of Maryland."
Jack played for five years at the club level (Long Island Athletic Club, four years, 1969 to 1972, Washington Lacrosse Club, one year, 1968). In 1971, he was a USCLA MVP for Long Island. Jack was an assistant coach at the U.S. Military Academy in 1969-1970 and also began a clinic at West Point for high school boys under Jim Adams. Jack officiated for one year at the high school level with the Long Island Lacrosse Officials Association.