36 In the fourth place, in order more easily to attain what We wish, to your fidelity and watchfulness We commend in a special manner the young, as being the hope of human society. Devote the greatest part of your care to their instruction; and do not think that any precaution can be great enough in keeping them from masters and schools whence the pestilent breath of the sects is to be feared. Under your guidance, let parents, religious instructors, and priests having the cure of souls use every opportunity, in their Christian teaching, of warning their children and pupils of the infamous nature of these societies, so that they may learn in good time to beware of the various and fraudulent artifices by which their promoters are accustomed to ensnare people. And those who instruct the young in religious knowledge will act wisely if they induce all of them to resolve and to undertake never to bind themselves to any society without the knowledge of their parents, or the advice of their parish priest or director.
Source: Humanum Genus (Vatican.va)