It is a sad day when parents find out, after the fact that their child's mind has been polluted by filth; filth assigned by a teacher.  Teachers are supposed to be trustworthy and wise.  Their job is to impart knowledge to those precious minds that have been entrusted to them.  They are not supposed to expose kids to sexually explicit materials that are against the morals of most responsible parents.  Regulations should be put in place, and teachers who display this lack of wisdom should also be fired on the spot!