I never believe in giving sex-morality teaching to children in schools. You are introducing them to sin. You are telling them about things they never knew before, and they are not “pure.” Therefore you cannot act on the assumption that such teaching will lead to good. That is the whole tragedy of modern education; it is based entirely on a psychological theory that does not recognize sin, instead of on New Testament teaching.
D. Martyn Lloyd-Jones, “Studies in the Sermon on the Mount,” volume 1, p.240