I suspect that there may be a correlation-without-causation issue here. I agree that smarter people are more likely to earn more and less likely to be poor. Some smart people are poor, but it's more likely that they won't be.
More women work now than did in the 1960s, and they have more career options. A two-earner family with two intelligent and educated earners will tend to earn a lot more than a two-earner family with only basic skills. The fact that more mothers work today could be one reason behind affluence of families with brighter parents today compared to 1962.
But the sad truth is that someone with an average IQ isn't super bright and that half the population is below that number. It's just a fact that some kids will not do super-well in an academic kindergarten environment. IMO, the kids aren't necessarily "failing." In at least some cases, the schools are failing to accept that some kids just need to go more slowly. But of course, respecting their abiliteis isn't allowed in a culture where everyone should go to college.
There will always be an achievement gap in life. It can't be closed. Some people are more talented than others. Some are luckier. Some have better connections. Etc. etc. The same is true in school. Some kids are just smarter. There's an achievement gap in sports, but no one seems to talk about closing it (presumably because most everyone admits that some kids just have more athletic talent).
I would prefer to put energy into being honest about people's abilities and helping them find jobs that fit with their talents, rather than pretending that we can just wish away differences in cognitive ability.
