Upon his return to civilian life after the Mexican-American War, Jackson taught at the Virginia Military Institute (VMI) from 1851 to the start of the American Civil War. He served as Professor of Natural and Experimental Philosophy (similar to modern day physics - it included astronomy, mechanics, acoustics, optics, and other sciences), which was a most difficult part of the mid-nineteenth century curriculum; many cadets found it almost impossible to master under the best of circumstances. He was generally acknowledged as an effective Instructor of Artillery Tactics, but anything more academic was not up Jackson's alley. Even with his record of tactical brilliance displayed later in the war, he was a failure as a teacher. Although highly intelligent, he could not convey the concepts to students. This inability, along with his humorless demeanor, soon branded Jackson as an unpopular faculty member, one who was the target of many student pranks. His reaction to students asking for assistance with classroom material or raising their hand in class to ask a question was met with the same result every time. Jackson simply stopped his current lesson, returned to the beginning of the lesson and repeated verbatim what he had just gone over with his students...with no additional explanation - simply rote memorization. Thus, classroom discussion became uncommon. With this, his students grew to dislike him very much, calling him "old Tom fool" and "old Jack." Another cadet nickname for Jackson was "old square box," mocking the exceptionally large size of Jackson's shoes. Jackson was such a bad teacher, that even Francis H. Smith, VMI Superintendent, later wrote of his teaching abilities: "As Professor of Natural and Experimental Philosophy, Major Jackson was not a success. He had not the qualifications needed for so important a chair. He was no teacher, and he lacked the tact required in getting along with his classes....His genius was in the Science and Art of War. He found a field for the display of this genius when the war opened in 1861." James Hyden, VMI class of 1857 wrote "Jackson's life, as a teacher, was singularly monotonous. He seldom opened his mouth except from absolute necessity. As Dick Taylor said "If silence is golden, Jackson was a bonanza." Hyden continued, "He had no turn for explanation, no talent for putting things in various points of view, so as to adapt them to the various mental conditions of his pupils. During the war he was often and highly commended for keeping his plans to himself; but I doubt if he could have explained those plans if he had done his best. If Davidson Penn, a portent of mischief, put on an uncommonly serious face and asked, apparently in good faith, "Major, can a cannon be so bent as to make it shoot around a corner?" the Professor of Artillery would show not the slightest sign of merriment or impatience, but would, after a moment of sober reflection, reply: "Mr. Penn, I reckon hardly." We could never decide whether his gravity on such an occasion was real or assumed, but, if it was assumed, it was certainly well acted."