14 Bishops should take pains that catechetical instruction-which is intended to make the faith, as illumined by teaching, a vital, explicit and effective force in the lives of men-be given with sedulous care to both children and adolescents, youths and adults. In this instruction a suitable arrangement should be observed as well as a method suited to the matter that is being treated and to the character, ability, age, and circumstances of the life of the students. Finally, they should see to it that this instruction is based on Sacred Scripture, tradition, the liturgy, magisterium, and life of the Church. Moreover, they should take care that catechists be properly trained for their function so that they will be thoroughly acquainted with the doctrine of the Church and will have both a theoretical and a practical knowledge of the laws of psychology and of pedagogical methods. Bishops should also strive to renew or at least adapt in a better way the instruction of adult catechumens.
Source: Christus Dominus (Vatican.va)