During his years at Choate, Kennedy was beset by health problems that culminated with his emergency hospitalization in 1934 at Yale New Haven Hospital, where doctors suspected leukemia. In June 1934, he was admitted to the Mayo Clinic in Rochester, Minnesota; the ultimate diagnosis there was colitis. Kennedy graduated from Choate in June of the following year, finishing 64th in a class of 112 students. He had been the business manager of the school yearbook and was voted the "most likely to succeed".