Gilpatric attended Poly Preparatory Country Day School from 1917 to 1920, when the family moved to White Plains, where he attended high school for two years before transferring to the Hotchkiss School, where he was a member of the remarkable class of 1924 that included Charles W. Yost, Paul Nitze, and Chapman Rose. His duties as a scholarship boy, which included waiting on tables and cleaning rooms, kept down his participation in extracurricular activities at Hotchkiss, but he was a member of the Cum Laude Society.