20 They should also be taught to use the aids which the disciplines of pedagogy, psychology, and sociology can provide, according to correct methodology and the norms of ecclesiastical authority. Likewise, let them be properly instructed in inspiring and fostering the apostolic activity of the laity and in promoting the various and more effective forms of the apostolate. Let them also be imbued with that truly Catholic spirit which will accustom them to transcend the limits of their own diocese, nation, or rite, and to help the needs of the whole Church, prepared in spirit to preach the Gospel everywhere. But since it is necessary for the students to learn the art of exercising the apostolate not only theoretically but also practically, and to be able to act both on their own responsibility and in harmonious conjunction with others, they should be initiated into pastoral work, both during their course of studies and also during the time of vacations, by opportune practical projects. These should be carried out in accordance with the age of the students and local conditions, and with the prudent judgment of the bishops, methodically and under the leadership of men skilled in pastoral work, the surpassing power of supernatural means being always remembered.
Source: Optatam Totius (Vatican.va)