Today's High School Grads Are Just as Good as Yesterday's

Tyler Cowen recommends a post from Steve Postrel attempting to explain why students are willing to pay ever higher amounts for a college degree. Unfortunately, it starts like this:

Typical graduate business school education has indeed become less rigorous over time, as has typical college education. But typical high school education has declined in quality just as much. As a result, the human capital difference between a college and high-school graduate has increased.

If anyone wants to present some evidence that high school education has declined over the past 30 years, I'm all ears. But as far as I know, there isn't any such evidence because it isn't true. I'm willing to buy the idea that there are specific things that high schools don't do as well as they used to — though if you have examples please provide some real evidence that they're true! — but overall? Most of the data I've seen suggests that today's high school grads know at least as much, and occasionally even more, than high school grads of the past.