Again, I think if you're looking to media for the explanation of why the lower class is doing poorly, you're looking in the wrong place.
Can I present one of a myriad of alternative hypotheses? All families have become 2 income families now, and while the wealthier can afford daycare, those with less money cannot. In addition, where there was once a gap between the rich and the poor, people are tending to marry within their own financial level more these days. So, that gap has increased.
A larger poor immigrant population is also placing a burden on our schools, which are very badly underfunded because no one ever is willing to pay more taxes to support schools.
In no way does any of this have anything to do with children attending R-rated movies.