59 Modesty will moreover suggest and provide suitable words for parents and educators by which the youthful conscience will be formed in matters of chastity. "Wherefore," as We said in a recent address, "this modesty is not to be so understood as to be equivalent to a perpetual silence on this subject, nor as allowing no place for sober and cautious discussion about these matters in imparting moral instruction." In modern times however there are some teachers and educators who too frequently think it their duty to initiate innocent boys and girls into the secrets of human generation in such a way as to offend their sense of shame. But in this matter just temperance and moderation must be used, as Christian modesty demands.
Source: Sacra Virginitas (Vatican.va)