Who is Tom Guthrie from Plainsong and what is their importance?

Tom Guthrie is described as both a good teacher and father, but he is encountering difficult challenges in both roles. When Guthrie's wife emotionally detaches from her family, Guthrie picks up the slack. When she abandons them, the changes and disruptions of her leaving make it impossible to create the stability and reliability he knows his young sons need.

At work, Guthrie faces completely different challenges..... the class bully, who is rude and violent, in addition to the boy's parents, who think their son can do no wrong. Guthrie receives support from the school's principal, but the parents embark on a relentless vendetta against Guthrie.