Now, its not only problematic that both these arguments were wrong, but that there was very good data explaining the real cause of the spike and subsequent drop in crime rates. Look at this chart of single mothers and crime rates v time.
Now look at this chart.
The effects of lead on brain development and its links to lower IQ, antisocial behavior and impulse control are well documented and the link to criminal behavior has been known for well over 2 decades. This makes it particularly embarrassing for Levitt, who published his abortion research in 2001. He admits now that his statistical methods were flawed, but not that he basically ignored a much more robust data set and theory which pointed to lead as the key factor. Though clearly Levitt has done some good work, I've found his popular writing to be driven by sensationalism, ego and money. "Freakonomics" is a brand more than any kind of science.
But the real message here is if we want to decrease crime rates and increase academic achievement continued effort into urban lead abatement is probably one of the most effective ways. And also, a clever narrative explanations can be very convincing and quickly become conventional wisdom accepted by all the Very Serious People while still being completely wrong.