Crime.  What crime requires a 'sentence' of parenting classes?  If they have no other children, what is to be gained by sending them to "parenting classes"?

If you get someone pregnant or become pregnant yourself what law requires you to attend 'parenting classes"?

Responsibility is a different issue.  Monetary responsibility may attach in some cases.   I'm not sure how threatening to kill the principal and other students results in monetary damage that the parents should have to pay, though.