From 1915 to 1927, Henri was a popular and influential teacher at the Art Students League of New York. "He gave his students, not a style (though some imitated him), but an attitude, an approach, [to art]." He also lectured frequently about the theories of Hardesty Maratta, Denham Waldo Ross, and Jay Hambidge. (Henri's interest in these men, whose ideas were in fashion at the time but were not taken seriously later, has proved to be "the most misunderstood aspect of [Henri's] pedagogy"). Maratta and Ross were color theorists (Maratta manufactured his own system of synthetic pigments), while Hambidge was the author of an elaborate treatise, Dynamic Symmetry, that argued for a scientific basis for composition. Henri's philosophical and practical musings were collected by former pupil Margery Ryerson and published as The Art Spirit (1923), a book that remained in print for several decades. Henri's other students include George Bellows, Arnold Franz Brasz, Stuart Davis, Edward Hopper, Rockwell Kent, Henry Ives Cobb, Jr., Lillian Cotton, John Sloan, Minerva Teichert and Yasuo Kuniyoshi.