It is absolutely incumbent upon the school to notify, involve and engage the parents in anything that has a potential negative effect on their children.  Sexually explicit material should NEVER be used or brought into the school whatsoever.  Sex does not belong in the school, but in the home with the parents or grandparents.  There is no reason for elementary school children to be de-sensitized or become familiar with sexual encounters or engagement.  They need to have a healthy contempt for EVERYONE that attempts to engage them in sex activity.  It is a very slippery slope into pedophilia and trafficking.