After an explosive argument with a schoolmaster, the 13-year-old Carpenter was expelled from school. He was dissatisfied with the limits of Moretown, and left home to live and study law under the tutelage of family friend (and future Vermont governor) Paul Dillingham in nearby Waterbury. For four years Carpenter attended the local grade school while absorbing Dillingham's law library. Having received an appointment to the United States Military Academy through Vermont Congressman John Mattocks, Carpenter continued his studies, but he disliked military life and resigned in August 1845, citing poor health.