In the book holes what was Mr role?

In the novel "Holes" by Louis Sacher, Mr. Sir (Stanley Yelnats IV's camp counsellor at Camp Green Lake) is the main antagonist. He appears to maintain strict control over the camp's juvenile delinquents, frequently using violent and abusive methods to enforce discipline. Stanley repeatedly conflicts with Mr. Sir throughout the novel, mainly because of his unfair and unjust treatment of both Stanley and the other campers.