From my own recollection of the case, this appears to have been a "doctors & nurses" or "show me yours and I'll show you mine" game that may have been taken a bit far by the children and an over reaction by the girl's parent and the authorities.
Children have experimented in this way for generations, much to the consternation of the parents who find out, but seldom does it cause problems.

Also, there appears to have been none of the sadistic visciousness of the Bulger or more recent Doncaster cases.