Who is David Henskin from A Map of the World and what is their importance?

Henskin is employed as principal at the Blackwell Elementary School. He is described as a formidable man, with gray hair, oily skin, and old-fashioned glasses. Ready to retire, Henskin doesn't assist Alice when she approaches him about Robbie Mackessy. After Alice is arrested for sexually abusing Robbie, Henskin denounces her.