Via Tyler Cowen, Scott Carrell and James West have done a thought-provoking little study of student achievement in college-level courses. They use data from the U.S. Air Force Academy, where students are randomly assigned to professors in a wide variety of core courses; syllabi and exams for the courses are identical; exams are graded communally; and students are randomly assigned to professors for both introductory and required follow-on courses. Their conclusion:
Our results indicate that professors who excel at promoting contemporaneous student achievement, on average, harm the subsequent performance of their students in more advanced classes. Academic rank, teaching experience, and terminal degree status of professors are negatively correlated with contemporaneous value added, but positively correlated with follow-on course value-added. Hence, students of less experienced instructors who do not possess a Ph.D. perform significantly better in the contemporaneous course, but perform worse in the follow-on related curriculum.
All the usual caveats apply. This is just one study. It's for college-level instruction. The introductory class is Calculus I and the follow-ons are various math and engineering courses. There's quite a bit of clustering in the middle. And there's always the chance that the researchers failed to control for something important. Still, pretty fascinating! As the chart on the right shows, professors who produced high-scoring students in their introductory courses (shown on the x-axis) also tend to produce students who score poorly in follow-on classes (y-axis). The obvious parallel here is to the results of standardized testing in elementary and high schools:
One potential explanation for our results is that the less-experienced professors may teach more strictly to the regimented curriculum being tested, while the more experienced professors broaden the curriculum and produce students with a deeper understanding of the material....Another potential mechanism is that students may learn (good or bad) study habits depending on the manner in which their introductory course is taught. For example, introductory professors who “teach to the test” may induce students to exert less study effort in follow-on related courses.
The researchers were only able to do this study properly because of the unusual conditions at the Air Force Academy. Still, it's provocative. One of the longtime problems with various high-stakes testing regimes has been the fact that although they often produce good results in early grades, these results usually wash out by the end of middle school. This study suggests that this problem might actually be built into the system.
On the other hand, it may also do no more than confirm the long-known fact that new teachers tend to be considerably less effective than more experienced teachers regardless of the type of curriculum. More studies, please.
UPDATE: For more, see Jessica Calefati's piece about the attempt by Florida and other states to pay teachers based on student scores on standardized tests. One problem: data on elementary school test performance is hard to judge because, unlike the Air Force Academy, kids aren't assigned randomly to classes.