To be a thorough success the co-education school must include sex education in its curriculum. The children of the most advanced parents seldom get it at home, and they come to school with the old attitude to sex. Sex education does not mean telling children where babies come from; it should dwell mostly on the psychological side of the question. The child ought to learn the truth about its sex instinct. Most important of all, the child who has indulged in auto-eroticism ought to be helped to get rid of his or her sense of guilt. This sense of guilt is the primary evil of self-abuse; abolish it, and the child is on the way to a self-cure. How many children can go to their teacher and make confession of sex troubles? Very few. It is the teachers' fault; they set themselves up as moralists, and a moralist is a positive danger to any child. Not long ago I was addressing a meeting of teachers in south London. At question time a woman challenged me. "You have condemned moralists," she said; "do you mean to say that you would never teach a child the difference between right and wrong?" "Never," I answered, "for I do not know what is right and what is wrong." "Then I think you ought not to be a teacher," she said. "I know what is right for me, and wrong for me," I went on to explain, "but I do not know what is right and wrong for you. Nor do I presume to know what is right or wrong for a child." I was pleasingly surprised to find that the meeting roared approval of my reply. * * * * * Macdonald had to attend a funeral to-day, and he asked me if I would take his classes for an hour. I gladly agreed. "Give them a lesson on psychology," he said; "it will maybe improve their behaviour." I went over to the school at two o'clock, and Mac introduced me, although I had already made friends with most of the children in the playground and the fields. Mac then went away and I sat down at his desk. "We'll have a talk," I said, "just a little friendly talk between you and me. I want to hear your opinions on some things." They looked at me with interest. "Why," I said, "why do you sit quiet in school?" Andrew Smith put up his hand. "Please, sir, 'cause if we don't the mester gies us the strap." "A very sound reason, too," I commented. "And now I want to ask you why you sometimes want to throw papers or slate-pencils about the room." "Please, sir, we never do that," said little Jeannie Simpson. "The mester wud punish us," said another girl. "But," I cried, "surely one of you has thrown things about the room?" Tom Murray, the bad boy of the school (according to Mac), put up his hand. "Please, sir, I did it once, but the mester licked me." "Why did you do it, Tom?" Tom thought hard. "I didna like the lesson," he said simply. I then went on further. "Now I want you all to think this out: was Tom being selfish when he threw paper, or was he unselfish?"