Graduating from Rockford West High School, Gentry led the Warriors to the IHSA state championship during consecutive seasons in 1955 and 1956.
[2] Ironically, his team would complete the Illinois state championship by defeating fellow Big 8 Conference opponent, Elgin by a final score of 61 to 59 in a thriller that witnessed arguably the most unique play in a state championship known as the "6-Point Second"[3] In the four game tournament, Gentry would be fourth of all scorers with 64 points, averaging 16 points per game.
During the four game tournament, Gentry would be tenth of all scorers with 50 points and be named to the all-tournament team with teammates John Wessels and Don Slaughter as well as Vaughn and Jackson.
[11] Gentry's final year of basketball was the 1959–60 season, his Hawkeyes team finished their schedule with an overall record of 14 and 10, sixth place in the Big Ten.
Based on this, Gentry decided to continue his education at Iowa, earning his Juris Doctor degree in 1964, with the pursuit of becoming an independent lawyer.