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Covering fewer topics in greater depth--studying electricity in several different ways, for example--improves physics pedagogy, according to Philip Sadler's research.Illustration by Tracy Mitchell

"High-school physics teachers try really hard; lots of them are great teachers doing great things with students," says Philip Sadler, Ed.D. '92, assistant professor of education. "It's just that the things they do don't result in better performance in college physics. The kids may be more comfortable with physics; they may learn how to read newspaper articles about physics; they may learn to do experiments. But what they don't get is the type of course that really helps them later on."

One in four high-school students takes physics--about 700,oo0 annually. Physics is "the pinnacle of high-school science, the jewel in the crown," says Sadler, who also directs science education at the Harvard-Smithsonian Center for Astrophysics. Approximately 360,000 students nationwide take introductory college physics each year. Those who don't do well often abandon science, closing the door on careers in engineering, medicine, and research.

Previous studies have found that students who took high-school physics outperformed those who didn't by six points, or about half a grade level. But these studies were limited to a single college or university and did not account for demographic variables. So Sadler, along with Graduate School of Education doctoral candidate Robert Tai, scrutinized the backgrounds and physics experience prior to college of 1,933 students at 18 colleges. What their survey found challenges common wisdom: in college physics courses, those who took high-school physics were only one percentage point above those who didn't.

Demographics matter. For instance, white and Asian students perform better than Native American, black, or Hispanic students in college physics. Suburban students and those with well-educated parents also have an advantage. Overall
grade point average and a previous calculus course predict strong performance in college physics--even without taking physics in high school. "This is very shocking," says Sadler. "Not shocking to college professors who have been saying all along that high-school physics doesn't matter. But shocking to the high-school physics teachers."

Some teachers have blamed the findings, which appeared this spring in The Physics Teacher, on elitism. For example, one woman e-mailed Sadler to point out that most of her "cherubs" will not be attending Harvard: "I'll bet if you checked the students that go to the more plebeian universities where my middle-class scholars tend to go, you will get different results." (Actually, Sadler sampled students from nine public state institutions, eight private colleges, and one national military academy; no Ivy League colleges were included.)

To better prepare students for college, says Sadler, high-school physics teachers should cover fewer concepts in more depth, especially mechanics, the focus of first-semester college physics. Sadler found that students who did not have physics textbooks in high school did much better in college. "The textbook has a kind of invisible control over the course, in terms of pumping it full of so many topics," he says. Because the United States has no national curriculum for physics, no mandatory national testing, and hence, "so little accountability, teachers often try to seek it themselves. They feel a sense of accomplishment if they finish the whole textbook," Sadler says.

Although the amount of physics homework in high school makes no significant difference, students who take the more rigorous advanced placement physics course or a second year of physics generally score higher in college than those with one year of "regular" high-school physics (by two and three more points, respectively). Taking introductory physics after the freshman year and having a professor of the same gender also improve performances.

Next, Sadler hopes to get funding to study secondary education in chemistry, biology, and earth science. Like their physics colleagues, high-school teachers in those subjects believe their courses ready students for college science. But college professors in all the sciences often lament the inadequate preparation of their students. "When you look at the high-school textbooks in chemistry and biology, they're even more bloated than the physics textbooks," says Sadler. "I know a lot of science, but when I look at an introductory biology book, I couldn't learn all that stuff in a year. And I'm a college professor. What about some poor tenth-grader?"

~ Kathleen Koman

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