Some counties actually require it, but for the most part the Judge that is trying the case will decide whether parents of minor children have to attend parenting classes.
Keep in mind that there are several different kinds of parenting classes with differing styles and focuses. For example, while some classes focus primarily on the children, others are more geared toward the parents. The price range for these courses can range from $30 to $75 and they typically last anywhere between 4 hours and 15 hours.