Hoelzel was of great importance for the development of modern art in Germany. In 1892 he opened a painting school in Dachau near Munich, where, among others, Emil Nolde was a student. Through his theoretical and didactic talent and his work, he attracted a large circle of artists, who later became famous, such as Max Ackermann, Willi Baumeister, Johannes Itten, Ida Kerkovius and Oskar Schlemmer. His trailblazing teachings on the artistic media and his colour theory reached the Bauhaus courses by way of his students.