What Do College Students Know? By this professor’s calculations, math skills have plummeted

Stephen Wilson:

Professors are constantly asked if their students are better or worse today than in the past. I conducted an experiment to try to answer that question for one group of students.
For my fall 2006 course, Calculus I for the Biological and Social Sciences at Johns Hopkins University (JHU), I administered the same final exam I had used for the course in the fall of 1989. The SAT mathematics (SATM) scores of the two classes were nearly identical, and the classes contained approximately the same percentage of the Arts and Sciences freshman class.
The content of the calculus I course had not changed and, from a math standpoint, using the old exam was completely appropriate.
The average exam score for my 2006 calculus I class was significantly lower than for my 1989 class. Comparing the effects of scaling in the two years reveals the extent of the decline. In my 1989 class, 27 percent of students received As on the test and 23 percent Bs. When I graded my 2006 class on my 2006 scale, 32 percent received As and 37 percent Bs. But if I instead graded my 2006 class on the 1989 scale, only 6 percent would have received As and 21 percent Bs. If I graded the 1989 class on the 2006 scale, 52 percent would have received As and 26 percent Bs.
Why did my 2006 class perform so poorly? With the proliferation of AP calculus in high school, one might think that the good students of 2006 place out of calculus I more frequently than did their 1989 counterparts. However, in 1989, 30 percent of the Arts and Sciences freshmen either took the harder engineering calculus course or a higher level mathematics course (calculus II or III, linear algebra, or differential equations). The percentage in 2006 is only 24 percent.