@FOUND SOUL,
I think the notion of washing a child's mouth out with soap is absolutely abhorent and any parent or guardian accused of this practice should, at the very least, be forced to undergo counseling. For one thing, it's a practice that could be quite hazardous to a child's health and well-being, and I don't mean just emotional well-being.
Back in the 19th Century, when the practice was apparently wide-spread, it was not only hazardous to a child's health but had the potential of being a fatal mistake. Virtually all soap back in those days was made with lye, which, taken internally, can be a deadly poison. This is no longer true and if you leave a bar of soap out overnight, you'll find that small night critters e.e. mice have nibbled on it; they find it nutritious. It's still a bad idea to subject any child to this type of humiliation.
Most children who swear do so in imitation of adult speech they have heard and are quite unaware that certain kinds of speech is inappropriate in certain venues and situation. They should be
educated as to this fact, not
punished for behavior that they scarcely realized was wrong.