Then let's cahnge the context to " bad marriages " instead of bad parenting . In our school district the single parent percentage borders around 50%. No supervision = time to party hardy till MOM gets home from work or wherever she was that day( % more than dad cause he doesn't live with the kids .).
It really does come down to parenting and doing that right. There is nothing else to pin it on -- who else is raising the kids and has responsibility for them? Single moms with a clue get neighbors or other family members (even those 200+ miles away) to check on the kids. Church groups also help out if asked.
I know this works - I was the kid in that environment and what I outlined above DOES work. Especially if the kid is encouraged to get a job at age 15 to keep him out of trouble :-)