There are two well-known documents in the history of education that frame the period covered by this study. The first is a letter written by the bishop and scholar Hildebert of Lavardin to William of Champeaux congratulating William on his ‘conversion’ from secular to Christian philosophy. The letter was prompted by William's decision to leave his role teaching in Paris in order to found a new community of Augustinian canons just outside the medieval city in c.1108. Given that William's teaching in Paris had been conducted whilst he was an archdeacon at the Cathedral of Notre Dame, the distinction between secular and Christian in this context may seem strange to modern readers. Hildebert referred to the subject of William's study, but the idea of conversion is also representative of a broader shift in which, following the monastic reforms of the late eleventh century, teaching in monasteries was increasingly for those intending to become monks, whilst schools associated with cathedrals offered training for those seeking other careers. Although Hildebert praised William's move, he encouraged him to continue his teaching. William followed Hildebert's advice, founding a school open to those not intending to join the community at his new abbey of Saint Victor, and teaching at both collegiate and cathedral schools boomed during the twelfth century. At the other end of the period of this study, the incorporation of the first universities in the early thirteenth century marked the recognition of the power of teachers and students in cities including Paris. The university at Paris was first recorded as such in 1215 when rules were laid down concerning the instruction of all masters. In the course of the long twelfth century, pedagogical practices including the facilities for and locations of teaching, the status of teachers, the applications of learning and the role of the Church in controlling teaching were all challenged. Some of these contests were subtle and developed over time; others, such as trials for heresy, provided moments of drama and apparent crisis. As Philippe Delhaye, Stephen Ferruolo, Stephen Jaeger and Ian Wei, amongst others, have explored, many changes in educational practice were fiercely debated, which in turn led to the creation of records of attitudes to education in both words and images.