His older brother Joe Jr. was already at Choate for two years and was a football player and leading student. Jack spent his first years at Choate in his older brother's shadow and compensated with rebellious behavior that attracted a clique. Their most notorious stunt was exploding a toilet seat with a powerful firecracker. In the next chapel assembly, the headmaster, George St. John, brandished the toilet seat and spoke of certain "muckers" who would "spit in our sea", leading Kennedy to name his group "The Muckers Club", which included roommate and lifelong friend Lem Billings.[18]

The Kennedy family in Hyannis Port, Massachusetts, with JFK at top left in the white shirt, 1931
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.[19] In June 1934, he was admitted to the Mayo Clinic in Rochester, Minnesota; the ultimate diagnosis there was colitis.[19] Kennedy graduated from Choate in June of the following year, finishing 64th in a class of 112 students.[11] He had been the business manager of the school yearbook and was voted the "most likely to succeed".