One of the most important functions of monasteries was as schools. Monastic schools were well attended (mostly by boys). Some of the students were treated as foster children by the monks, living in the care of another family until they were ready to return to their homes and adult responsibilities. Many noble warrior fathers seem to have thought that their sons would be safer in a monastery than at home. Students had to find and prepare food for the monks and help out with the business of running the monastery. But most of their time was spent studying and working.

By the sixth century, Irish schools had a firm curriculum. Students studied Latin grammar, biblical exegesis, and the ecclesiastical calendar. A monastery's library would contain several basic texts, including the Bible (the Latin Vulgate, translated by St. Jerome), various commentaries on Scripture, Jerome's book on early Church writers called De uiris illustribus, and a church history by Eusebius. The computation of the ecclesiastical calendar was of special interest to Irish monks and medieval religious scholars in general, and big monasteries would stock several works on the subject. The seventh-century scholar Columbanus mentioned calendrical problems in several of his letters.