While they're eating dinner, the boys of St. Alban's listen to their Master reading from the lives of the saints in Latin.
The Master's voice is the only one that is allowed to be heard at mealtimes, where absolute silence among the boys in insisted upon. The boys study in a monastery, where for most of the day, the monks go about their business in complete silence. The idea is that this will make it easier for them to focus on serving God, which is the whole purpose of joining a monastery in the first place.
Stories of saints' lives are primarily used for the purposes of moral instruction. The Master hopes that by recounting such tales, his pupils will follow the saints' examples and lead godly lives.