Strong agreement with my colleague Paul Gessing on his blog A Free Market in Education? David Brooks's assertion that "the market is failing to supply enough human capital," not only fails on Gessing's point (the education "market" is almost entirely controlled by government.) But, perhaps audaciously, I'd ask, Who's to say if there's "enough" human capital? Who's to say that formal education is the optimal way to develop human "capital," a term that is utterly squishy. I suspect Brooks means something more like "skills and abilities," but whatever.
Citing dropout rates from high school and college seems weak proxies at best for developing the workforce's skills and abilities, and weaker still for productivity. Most productivity measures that I've seen are improving, so Brooks seems to be making some rather major logic leaps.
And, of course, what are the reasons why drop-out rates have increased? Funding "education" more might be a case of throwing good money after bad unless there's good reason to believe that this is a resource problem.