But they're not horrendous?
That's because it boils down to parenting.
It's not really got much to do with 0, 1 or 2 parents working. Nor on single parenthood. Nor any of the other reasons often touted.
But we're not allowed to point the finger at parents and say, "Your child behaves like this because you're just a bit crap," so all these other reasons are bandied about.
If you're a good parent then you're a good parent. No matter what your socio-economic background, your education, your intelligence level, your social mobility etc. If you're a lazy parent, then you're a lazy parent.
If I look at the children I've taught in isolation, it would be easy to say, "You behave like x because..." and insert any reason - cash rich/time poor and over indulged; single parent; both parents/neither parent works etc.
But the truth is that it doesnt matter what family set up/dynamic we can think of, there will always be another child/family who is the same but where the parents have made different choices and prioritised their child/ren and whose children won't behave badly.
I worked long hours as a single parent and a teacher. I still listened to my children read, made bathtimes a bonding experience, took an interest in them. I used to sit in the car when my young daughter had ballet on my laptop planning. I played with them, made dens, walked in the park, taught them to cook.
As a teacher, I always find the first parents evening of the year very revealing. Additional needs aside, I have yet (in 20 years of teaching) to meet a parent and think, "Huh. You weren't what I expected!" Good and bad, you meet the parents and everything about the child becomes clear.