Who serves as Garp's mentor during his time at Steering in the novel, The World According to Garp?

Mr. Tinch is the stuttering, halitosis-cursed, English teacher who becomes a kind of mentor to Garp while he attends Steering School. His nickname among the students is "Stench." When Tinch asks Garp if his breath stinks in front of the class, Garp denies it to spare his teacher from embarrassment.