Byron received his early formal education at Aberdeen Grammar School, and in August 1799 entered the school of Dr. William Glennie, in Dulwich. Placed under the care of a Dr. Bailey, he was encouraged to exercise in moderation but could not restrain himself from "violent" bouts in an attempt to overcompensate for his deformed foot. His mother interfered with his studies, often withdrawing him from school, with the result that he lacked discipline and his classical studies were neglected.
In 1801, he was sent to Harrow, where he remained until July 1805. An undistinguished student and an unskilled cricketer, he did represent the school during the very first Eton v Harrow cricket match at Lord's in 1805.
His lack of moderation was not restricted to physical exercise. Byron fell in love with Mary Chaworth, whom he met while at school, and she was the reason he refused to return to Harrow in September 1803. His mother wrote, "He has no indisposition that I know of but love, desperate love, the worst of all maladies in my opinion. In short, the boy is distractedly in love with Miss Chaworth." In Byron's later memoirs, "Mary Chaworth is portrayed as the first object of his adult sexual feelings."
Byron finally returned in January 1804, to a more settled period which saw the formation of a circle of emotional involvements with other Harrow boys, which he recalled with great vividness: "My school friendships were with me passions (for I was always violent)." The most enduring of those was with John FitzGibbon, 2nd Earl of Clare — four years Byron's junior — whom he was to meet unexpectedly many years later in Italy (1821). His nostalgic poems about his Harrow friendships, Childish Recollections (1806), express a prescient "consciousness of sexual differences that may in the end make England untenable to him." Letters to Byron in the John Murray archive contain evidence of a previously unremarked if short-lived romantic relationship with a younger boy at Harrow, John Thomas Claridge.
The following autumn, he went up to Trinity College, Cambridge, where he met and formed a close friendship with the younger John Edleston. About his "protégé" he wrote, "He has been my almost constant associate since October, 1805, when I entered Trinity College. His voice first attracted my attention, his countenance fixed it, and his manners attached me to him for ever." In his memory Byron composed Thyrza, a series of elegies. In later years, he described the affair as "a violent, though pure love and passion". This statement, however, needs to be read in the context of hardening public attitudes toward homosexuality in England and the severe sanctions (including public hanging) against convicted or even suspected offenders. The liaison, on the other hand, may well have been "pure" out of respect for Edleston's innocence, in contrast to the (probably) more sexually overt relations experienced at Harrow School.
Byron spent three years at Trinity College, engaging in sexual escapades, boxing, horse riding and gambling. Also while at Cambridge he formed lifelong friendships with men such as John Cam Hobhouse, who initiated him into the Cambridge Whig Club, which endorsed liberal politics, and Francis Hodgson, a Fellow at King's College, with whom he corresponded on literary and other matters until the end of his life.