The White Feather by P. G. Wodehouse

Sheen, a member of Seymour's House at Wrykyn School, flees from an unexpected assault by town boys. His colleagues wade into the fight with relish, acquiring bruises and sore heads, but in the fracas, Sheen is missed, and the story makes the rounds of Wrykyn that when blows were traded, Sheen "funked it."Honor in such institutions depends on reliably standing with your House. As punishment for his defection, Sheen is "cut" - treated as if he did not exist.In a later expedition into town, Sheen is set upon by the town bullies and finds that when retreat is no option, he can take their blows and fight against odds. Seeing his pluck, bystander Joe Bevan, an ex-champion boxer, offers to tutor Sheen.Surprisingly, Sheen finds he has a knack for boxing. And with that discovery comes a plan: he will fight for his House in the Lightweight division and win back his honor.But the best-laid plans... may go awry!Wodehouse, a humorist, picks up the sober topic of cowardice but treats it with his customary panache.