Who is Herr Geer from The Last of the Just and what is their importance?

Herr Geer is Kremer's replacement at Ernie's school. He is described as a vicious, mean little man, who takes pleasure in torturing and humiliating his Jewish students. Geer's job is to prepare his Aryan students for their role in the new Fatherland under Adolf Hitler, and he takes it seriously.