 He enrolled at the Art Students League for a two-year program during 1905–07 under George Bridgman, Norman Rockwell's teacher.A student colleague later persuaded Koerner to apply to Howard Pyle's illustration school in Wilmington.Koerner's exposure to Howard Pyle was significant, but his student colleagues also had much to offer and he shared techniques and styles with the likes of N. C. Wyeth, Harvey Dunn, Frank Schoonover and Stanley Arthurs.