Dunn spent the bulk of his teaching career in New York at the Grand Central School of Art and The Art Students League, but began his life long love afair with teaching in 1915 at a school he founded, the Leonia School of Illustration. It was here that he taught Dean Cornwell, who once said of Dunn's teachings "I gratefully look back on the time when I was privileged to sit at Harvey Dunn's feet . . . [he] taught art and illustration as one. He taught it as a religion - or awfully close to such."
Here are two interesting reads
Harvey Dunn's Class Notes by Charles J. Andres
An Evening in the Classroom