88 Perfect schools are the result not so much of good methods as of good teachers, teachers who are thoroughly prepared and well-grounded in the matter they have to teach; who possess the intellectual and moral qualifications required by their important office; who cherish a pure and holy love for the youths confided to them, because they love Jesus Christ and His Church, of which these are the children of predilection; and who have therefore sincerely at heart the true good of family and country. Indeed it fills Our soul with consolation and gratitude towards the divine Goodness to see, side by side with religious men and women engaged in teaching, such a large number of excellent lay teachers, who, for their greater spiritual advancement, are often grouped in special sodalities and associations, which are worthy of praise and encouragement as most excellent and powerful auxiliaries of "Catholic Action." All these labor unselfishly with zeal and perseverance in what St. Gregory Nazianzen calls "the art of arts and the science of sciences," the direction and formation of youth. Of them also it may be said in the words of the divine Master: "The harvest indeed is great, but the laborers few." Let us then pray the Lord of the harvest to send more such workers into the field of Christian education; and let their formation be one of the principal concerns of the pastors of souls and of the superiors of Religious Orders.
Source: Divini Illius Magistri (Vatican.va)