Teaching at Académie Julian was nearly always done by pairs of teachers, alternating months of critique, these pairings were not always harmonious. This was not the case with Boulanger and Lefebvere however. One American student noted "The training they enforce is liberal; their methods and their manner are never insisted on.... The one insists on finesse of line and of articulation; the other on the energy of expression and individuality of the model; so these two men supplemented each other."
Among their students were George Bridgman, Frank Vincent Dumond, John Henry Twachtman, Edward Tarbell etc.
For more information check out "The Lure of Paris" by H. Barbara Weinberg
Gustav Boulanger "The Slave Market" (1888) "Reception of an Emir" (1871)
Jules-Joseph Lefebvre: "Ophelia" (1890) "The Japonaise" (1882)