Tuesday, January 31, 2006

Causation, correlation, and algebra 

Joanne Jacobs notes the effects of a California rule that students cannot complete high school without passing algebra. Three-quarters of students who fail the course once also fail a repeat attempt. 61% of first-time students took D's or F's in the course. And as a results, students are leaving:
"It triggers dropouts more than any single subject," said Los Angeles schools Supt. Roy Romer. "I think it is a cumulative failure of our ability to teach math adequately in the public school system."

Now one problem seems quite clear to me: Just having students retake the course isn't going to help. If you are serious about math education as giving graduates "a better education and groom more graduates for college and high-level jobs," you need to address the lack of preparation in the first eight grades. That involves both a review of what is being taught in K-8 and something to remediate the students already in the system. Creating a pre-algebra course for students who fail freshman algebra should be a no-brainer ... assuming it is funded. Jacobs:
At Downtown College Prep, the San Jose charter school that's the subject of my book, ninth graders who are more than two years behind in math skills take a "numeracy" course to brush up on the basics while also taking algebra. Most flunk algebra the first time they take it but pass in summer school or 10th grade. ... For LA high schools to keep students in algebra year after year without teaching basic math skills is ludicrous.

Yes. But it seems to me as well that the data on algebra skills and college success (or career success) suffers as well from the old chestnut that "correlation does not mean causation". The lack of algebra skills among these students is not random; failing algebra can be a marker for a whole set of other issues that may make college or career success less likely. While there are plenty of studies that indicate that a students with a rigorous high school curriculum do better in college, that does not mean that it's causative. We know that kids that can hit a 90-mph fastball in high school are more likely to become major league players, but that doesn't mean you make any kid a player by putting him in a batting cage with the machine turned up to 90. It's this failure to distinguish between necessary and sufficient conditions that make for bad policy decisions.